Free software should be free!
That’s why people choose it instead of commercial software. If you don’t have the means, the passion and the time to develop free software then you better don’t do it or make it commercial software. Because when you call a product free, then people expect it to be really free and they don’t want all kinds of hidden costs.
Yes. Many free programs have hidden costs that you only discover after you have been using the program a time. For example some developers after they get their software to a certain popularity level start to ask for “donations” even to fix bugs in their software. Not to mention that documentation for most of these start with a pledge for donations and for some that is the only thing you can find in the documentation.
This is not fiction, this is happening for real. I started to use some plugins for one of the content management systems i use, only to learn that the developer will not fix the bugs in it unless he is paid for these fixes.
Don’t get me wrong, i know that the developer has to eat and pay the rent but not using these methods. This way even if someone had in mind to donate, it will certainly anger him enough to change his mind. If the user knew from start that this will cost money, maybe he would have choosen a commercial plugin with support included.
If you start to ask money then ask for new developments, feature requests, not for bug fixes! And if you started to ask money then label your software as commercial so you won’t mislead people when they make a choice.