@syzygy It is correct that just an `int main() { return 0; }` is insufficiently creative to qualify for copyright law, but you should offer a free license regardless in case it does turn out that the software is restricted by copyright, so you don't end up distributing proprietary software.

I find the true implementation and how it also implements false in the same source file quite creative, so it does qualify for copyright and therefore it is licensed under the GPLv3-or-later; https://git.savannah.gnu.org/cgit/coreutils.git/tree/src/true.c