You can't just freely receive donations and not pay any tax. There is definitely an argument that you are donating to ensure future development of the software,

You can't just freely receive donations and not pay any tax. There is definitely an argument that you are donating to ensure future development of the software, essentially quid pro quo. Edit: Wireguard literally make that case while soliciting donations >We're extremely grateful for all donations, which enable us to continue developing WireGuard as free open source software. We are happy to receive donations from interested companies who would like to see WireGuard development continue and thrive, as well as individual donations from folks who would simply like to say "thanks".