Maybe go for a license / ??? that allows for free use but requests payment for paid use

Actually, that would make it non-free (a.k.a source-available) software by FSF’s definition. You can do something like Qt (copyleft license for free, permissive license for a fee), but this doesn’t really work for a lot of software.

It’s easy to write, easy to build, produces lightweight and fast executables, and the type system is great. Why not rust?

This is precisely the problem that deploy-rs solves!