As in Mozilla stopped developing officially? Because I have seen active development on GitHub and monthly updates on their blog.

Mozilla stopped in 2020: https://news.ycombinator.com/item?id=24128865

The project limped along for a bit, then recently Igalia started putting resources into it: https://news.ycombinator.com/item?id=39269949

Yes, a while ago. But fortunately people continue. Just not with the billion dollar budget of Mozilla and with seemingly less traction. I have not heard of them in a while.

But I very much endorse both. And yes, in theory energy should be focused, but I rather have 2 smallish projects, but with potential, than one slightly bigger one, with fighting about direction all the time.

Yes, that's correct. It was later adopted by the Linux Foundation with some industry support: https://www.linuxfoundation.org/press/press-release/open-sou...