I’ve been considering getting one but I’ve read too many horror stories about them breaking

Bingo. Same with Beehaw and many others.

0.18 was a big change (for example websockets to http), I’d imagine future versions are unlikely to be so drastic and will allow Jerboa to be compatible with older versions

$0.14 per user per month is… Higher than I expected.

Yes it’s FOSS: https://github.com/dessalines/jerboa/blob/main/LICENSE

Unsure on the rest