Ah, yeah. I guess he created the official repo for this in January of this year. According to him, he's been working on this for 5 years. The very first commit he has in the repo is huge. It seems like he already had most of the code working already.

Personally, I don't think that's weird. I have several projects in private git repos. If I were to make any of those public, I would for sure copy stuff over to a new repo and ditch the old one.

Stoat does have voice and video and screensharing in their desktop+web clients at least, but as of this comment in August it still wasn’t implemented in mobile clients

Ah, I didn't know. Cool!

And also it wasn’t/isn’t enabled on their flagship instance due to the high cost of running a free video relay.

This makes sense. They need more money to keep the project going. That's why I don't totally mind Fluxer selling Plutonium. Open Source can't (fully) run on hopes and dreams. Actually, seems like Stoat doesn't have a donate button anywhere. Even just getting enough donations to rent a faster VPS would help. The main instance is slow. Which I understand why. It's just unfortunately that if someone compares them with Fluxer, Fluxer is gonna be faster. :/

Stoat is also AGPLv3; do they require copyright assignment?

Yeah, Stoat is also AGPLv3! I think they required a CLA when they were revolt. But not sure about today.