From WFG Wiki

The REAL ID Act of 2005, 119 Stat. 302, enacted May 11, 2005, modified U.S. federal law pertaining to security, authentication, and issuance procedures standards for the state driver's licenses and identification (ID) cards, as well as various immigration issues pertaining to terrorism.

The law sets forth requirements for state driver's licenses and ID cards to be accepted by the federal government for "official purposes", as defined by the Secretary of Homeland Security.

A number of states ID's have not been recognized as compliant. Most are on extension or waivers, but those begin to expire in 2016. DHS waiver list

The question has been raised whether a non-conforming ID may be used for purposes of identifying the parties to a federally insured loan or participating in federal real estate programs.

The answer appears to be "Yes" non-conforming IDs may still be used for these federal purposes. (when consistent with normal Identity verification standards) The Act defines "Official Purpose" this way

"(3) Official purpose.--The term ``official purpose includes but is not limited to accessing Federal facilities, boarding federally regulated commercial aircraft, entering nuclear power plants, and any other purposes that the Secretary shall determine."

Although the law gives the Secretary the unlimited authority to require a "federal identification" for any other purposes that the Secretary shall determine, as of this writing, we find no indication that this authority has been exercised beyond federal facilities, nuclear power plants and aircraft.