tldraw used to be FOSS but they changed the license in 2023. https://tldraw.substack.com/p/license-updates-for-the-tldraw...

BigBlueButton had to fork tldraw because of this. https://docs.bigbluebutton.org/new-features/#we-have-forked-...

See, I wasn't even familiar with this company and it sounds like my suspicion was accurate.