I have a very good and a bad news about this subject.
The good news is: The Seasteading Institute will accept bitcoin donations!
They send me their address by mail: 1FexWDptSXFWsZvdLoBckZgVFWytHjsSu8
I've asked them to add it to their donation page so you don't need to trust my word only.
The bad news is about the account I had opened in November in MyBitcoin to store the donations. It had received 50BTC from one donor. But that was a while ago, and I just cannot remember the password.
Yeah, I know, shame on me!
I tried creating another account in order to ask them help to recover this money. I sent them two messages but got no answer, and since a few days they have this message on their site:
Note: We are experiencing growing pains. Support will be degraded until we are able to upgrade our systems. Thank you for your patience.
I hope to be able to contact them once they are reachable again and recover these 50BTC. I apologize to whoever did that donation, I'm really sorry.