FreeFileSync Forum

A periodic pop-up on startup is a gross option in my opinion.

but on the other hand you have (at least in non-donate version) periodic pop-up about available new version. You could change that pop-up into a donate pop-up. I don't see a big difference.

Also, in my opinion, enforcing people to ...

The main problem to me is if that's even possible (from law point of view) to forbid distributing a program and using GPL license the same time? GPL allows you to distribute a program (at least according to that summary for lazy people: https://tldrlegal.com/license/gnu-general-public-license-v3 ...