Popular licenses undergoing DOSP like FSL and BUSL were written by lawyers -- very prominent ones in OSS such as Heather Meeker -- so I'd say they're very enforceable.

Ask your lawyer. Licenses matter to the degree the parties have good will and/or legal wherewithal. Nobody is going to enforce the terms of a license except the parties to the license. If it matters, you can litigate if you have the resources.

To me, a license people have questions about is probably a bad license. The exception being a license that is negotiated between lawyers for each party. Good luck.