The primary reason why it would be enforceable is that you need a license to run a program (copying to ram, as per https://en.wikipedia.org/wiki/MDY_Industries,_LLC_v._Blizzar...). A build program's license could thus include any type of conditions which dictate terms for usage, including what kind of license that project has.

The only limits are those inherent to copyright itself (https://en.wikipedia.org/wiki/Limitations_and_exceptions_to_...), and consumer protection laws. Consumer protection law would be the best guess as to limit what kind of conditions a product has after sale, but so far most legal system has chosen not to do so, and it get even more complex area when the product is given away for free.