Legal, yes. If we did decide to accept donations, any money that was earned would go straight back into maintaining the game - paying server costs (if we ever expand beyond the needs of my personal server), registering a domain name that doesn’t have my username in it, putting out advertising on other sites to attract more data, contracting out work to actually design those ads, that sort of thing.
The issue is whether the cost and time commitment of handling donations would be worth the effort. Our current player-base isn’t exactly huge, after all, and there’s a bit of work and red tape wrapped up in handling money for a project like this. Doable, but a real time commitment getting it in and sending it back out and, if it ended up coming down to that, distributing it among contributors.