It can be. You can release under a "source available" license barring it from being used (even compiled), derived, incorporated into other works, making it basically "for eyes only, or we sue you to oblivion".
Many people consider licenses as window decorations, but they are not.
So if anyone wants to put a past release online they are free to do so (unless there are parts of the code that were restricted before).
It would be prudent to remove branding where possible but that's mainly a precaution.
Many people lack this knowledge from my experience.
ADDED Unless it’s public domain and then it effectively is.
Personal use doesn't free you the obligations GPL brings, for example.
Well sure, but that's a really big caveat.