DFARS clause prohibiting DOD from requiring delivery of source code?

Nevermind.  I found it.  It is in DFARS 227.72, concerning Non-Commercial Computer Software, it says DOD cannot require the offeror to "relinquish rights . . . in computer software developed exclusively at private expense . . . "  I believe that means source code.

DFARS 252.227-7014 Rights in Noncommercial Computer Software, etc., paragraph (b)(3) is as follows:

(i) The Government shall have restricted rights in noncommercial computer software required to be delivered or otherwise provided to the Government under this contract that were developed exclusively at private expense.

(ii) The Contractor, its subcontractors, or suppliers are not required to provide the Government additional rights in noncommercial computer software delivered or otherwise provided to the Government with restricted rights. However, if the Government desires to obtain additional rights in such software, the Contractor agrees to promptly enter into negotiations with the Contracting Officer to determine whether there are acceptable terms for transferring such rights. All noncommercial computer software in which the Contractor has granted the Government additional rights shall be listed or described in a license agreement made part of the contract (see paragraph (b)(4) of this clause). The license shall enumerate the additional rights granted the Government.

Thanks, Neil Roberts!