Regarding donations and free games

Regarding donations and free games

This is a question that popped to my mind some days ago. Every now and then you see free software and games, that ask for donations to support further game development. This is all good and well, but what is the legal status regarding donations to projects and/or single persons? What would one need to be aware of (taxation, in what ways are donations considered income etc.) when asking donations for a project? I could not find a topic on this and I'm just wondering how this usually works.