Do credit unions have to play by the same regs as banks? (I already know that taxes and CRA don't apply to them.)

Generally, yes. Especially the consumer friendly ones, such as Regs DD, E, Z, B, etc.

Reg DD says it doesn't cover credit unions.

That surprises me, but I was on the loan side of the CU I worked at, so what do I know?

I do know that most (if not all) of the consumer lending related regs do apply.

Credit unions are subject to the Federal Truth-in-Savings Act of 1991.(Reg DD). As credit unions are federally insured by the NCUA - that agency overseas the regulation versus the FDIC for banks. Section 707 of the NCUA Rules and Regulations gives the specifics.

Because Congress noted that credit unions have some unique ways of handling interest on members' accounts, it decreed that NCUA would write a separate rule for them.