Drawpile

Drawpile is a Free and Open Source collaborative drawing program that lets multiple people draw, sketch, paint and animate on the same canvas simultaneously. You can get the program on https://drawpile.net.

For other ways to donate, take a look at https://donate.drawpile.org/.

That link also has more information where your money goes and how to get in contact, as well as tax information for donating from Germany, impressum, privacy policy etc.