Consent and Waiver to Credit Agreement by Deltek Systems, Inc. and Credit Suisse, Dated April 13, 2006

Exhibit 10.63

EXECUTION COPY

CONSENT AND WAIVER dated as of April 13, 2006 (this “Consent”), relating to the Credit Agreement dated as of April 22, 2005 (as amended, supplemented or otherwise modified from time to time, the “Credit Agreement”), among DELTEK SYSTEMS, INC., a Virginia corporation (the “Borrower”), the Lenders party thereto and CREDIT SUISSE (formerly known as Credit Suisse First Boston), as administrative agent (in such capacity, the “Administrative Agent”) and collateral agent for the Lenders.

A. Pursuant to the Credit Agreement, the Lenders and the Issuing Bank have extended, and have agreed to extend, credit to the Borrower.

B. The Borrower has not furnished to the Administrative Agent, as required by Sections 5.04(a) and 5.04 (c) of the Credit Agreement, its consolidated financial statements with respect to the year ended December 31,2005, accompanied by the audit opinion and accountants’ certificate required by such Sections (collectively, the “Financial Statements and Certificates”) and has not made any mandatory prepayment required by Section 2.13(d) of the Credit Agreement (the “2005 Excess Cash Flow Payment”).

C. Further, the Borrower has informed the Administrative Agent that it intends to make an interest payment in cash in respect of the Shareholder Notes in an aggregate amount of approximately $8,000,000 (the “Shareholder Notes Interest Payment”). Additionally, the Borrower has informed the Administrative Agent that it intends to refinance all of its outstanding Shareholder Notes (the “Shareholder Notes Refinancing”) with the proceeds of Incremental Term Loans to be made pursuant to an Incremental Term Loan Assumption Agreement in accordance with Section 2.24 of the Credit Agreement.

D. The Borrower has requested that the Requisite Lenders (as defined below) (i) waive, until May 15, 2006, (A) compliance by the Borrower with Sections 5.04(a) and 5.04(c) of the Credit Agreement and (B) any Default or Event of Default that may have arisen solely as a result of the failure of the Borrower to deliver to the Administrative Agent the Financial Statements and Certificates, (ii) waive (A) compliance by the Borrower with Section 2.13(d) of the Credit Agreement solely with respect to the 2005 Excess Cash Flow Payment and (B) any Default or Event of Default that may have arisen solely as a result of the failure of the Borrower to make the 2005 Excess Cash Flow Payment and (iii) consent to the making of the Shareholder Notes Interest Payment on or after the earlier to occur of (x) the date of the consummation of the Shareholder Notes Refinancing and (y) May 15, 2006 (such earlier date, the “Shareholder Notes Interest Payment Date”).

E. The Requisite Lenders are willing so to consent and to grant such waivers on the terms and subject to the conditions set forth herein.

F. Capitalized terms used but not defined herein shall have the meanings assigned to them in the Credit Agreement.

Accordingly, in consideration of the mutual agreements herein contained and other good and valuable consideration, the sufficiency and receipt of which are hereby acknowledged, the parties hereto agree as follows:

SECTION 1. Consent. The Requisite hereby (a) consent to the making of the Shareholder Notes Interest Payment on the terms described above on or after the Shareholder Notes Interest Payment Date, and (b) waive compliance by the Borrower with the provisions of Sections 6.09(b) and 6.09(c) of the Credit Agreement to the extent (but only to the extent) necessary to permit the making of the Shareholder Notes Interest Payment on or after the Shareholder Notes Interest Payment Date.

SECTION 2. Waivers. (a) Pursuant to Section 9.08(b) of the Credit Agreement, the Requisite Lenders hereby waive:

(i) subject to clause (c) below, (A) compliance by the Borrower with Sections 5.04(a) and 5.04(c) of the Credit Agreement and (B) any Default or Event of Default that may have arisen solely as a result of the failure of the Borrower to deliver to the Administrative Agent the Financial Statements and Certificate; and

(ii) (A) compliance by the Borrower with Section 2.13(d) of the Credit Agreement (solely with respect to the 2005 Excess Cash Flow Payment) and (B) any Default or Event of Default that may have arisen solely as a result of the failure of the Borrower to make the 2005 Excess Cash Flow Payment.

(b) In no way shall the waivers set forth in clause (a)(i) above be deemed to be a waiver of any matter disclosed in the Financial Statements and Certificates upon delivery thereof.

(c) The waivers set forth in clause (a)(i) above shall remain in effect through and including May 15, 2006, after which time such waivers shall automatically terminate and be of no further force or effect, and all rights and remedies with respect to the matters set forth in clause (a)(i) hereof of the Administrative Agent, the Collateral Agent and the Lenders under the Credit Agreement and any other Loan Document shall, without any further action by any person, automatically be reinstated as if such waivers set forth in clause (a)(i) hereof had not become effective.

SECTION 3. Representations and Warranties. To induce the other parties hereto to enter into this Consent, the Borrower represents and warrants to each of the Lenders, the Administrative Agent and the Issuing Bank that, alter giving effect to this Consent, (a) the representations and warranties set forth in Article Ill of the Credit Agreement are true and correct in all material respects on and as of the date hereof, except to the extent such representations and warranties expressly relate to an earlier date and (b) no Default or Event of Default has occurred and is continuing.

SECTION 4. Effectiveness. This Consent shall become effective as of the date set forth above on the date that the Administrative Agent shall have received counterparts of this Consent that, when taken together, bear the signatures of (a) the Borrower, (b) the Required Lenders and (c) Term Lenders holding a majority of the aggregate principal amount of outstanding Term Loans (the Lenders described in clauses (b) and (c) being referred to herein as “Requisite Lender”).

SECTION 5. Effect of Consent, Waiver and Agreement. Except as expressly set forth herein, this Consent shall not by implication or otherwise limit, impair, constitute a waiver of, or otherwise affect the rights and remedies of the Administrative Agent, the Collateral

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Agent, the Lenders or the Issuing Bank under the Credit Agreement or any other Loan Document, and shall not alter, modify, amend or in any way affect any of the terms, conditions, obligations, covenants or agreements contained in the Credit Agreement or any other Loan Document, all of which are ratified and affirmed in all respects and shall continue in full force and effect. Nothing herein shall be deemed to entitle any Loan Party to a consent to, or a waiver, amendment, modification or other change of, any of the terms, conditions, obligations, covenants or agreements contained in the Credit Agreement or any other Loan Document in similar or different circumstances. After the date hereof, any reference to the Credit Agreement shall mean the Credit Agreement, as modified hereby. This Consent shall constitute a “Loan Document” for all purposes of the Credit Agreement and the other Loan Documents.

SECTION 6. Counterparts. This Consent may be executed in any number of counterparts and by different parties hereto in separate counterparts, each of which when so executed and delivered shall be deemed an original, but all such counterparts together shall constitute but one and the same contract. Delivery of an executed counterpart of a signature page of this Consent by facsimile transmission shall be as effective as delivery of a manually executed counterpart hereof.

SECTION 7. Applicable Law. THIS CONSENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

SECTION 8. Headings. The headings of this Consent are for purposes of reference only and shall not limit or otherwise affect the meaning hereof.

SECTION 9. Expenses. The Borrower agrees to reimburse the Administrative Agent for all out-of-pocket expenses in connection with this Consent, including the reasonable fees, charges and disbursements of Cravath, Swaine & Moore LLP, counsel for the Administrative Agent.

SECTION 10. Acknowledgment of Subsidiary Guarantors. Each of the Subsidiary Guarantors hereby acknowledges receipt and notice of, and consents to the terms of, this Consent.

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IN WITNESS WHEREOF, the parties hereto have caused this Consent to be duly executed by their duly authorized officers, all as of the date and year first above written.

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IN WITNESS WHEREOF, the parties hereto have caused this Consent to be duly executed by their duly authorized officers, all as of the date and year first above written.

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SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005 AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006 RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED

SIGNATURE PAGE TO THE

CONSENT AND WAIVER DATED

AS OF APRIL 13, 2006, RELATING

TO THE DELTEK SYSTEMS, INC.

CREDIT AGREEMENT DATED AS

OF APRIL 22, 2005, AS AMENDED