As far as I can tell they are a FOSS project (AGPLv3) that runs on donations.

User experience when I first started using it about a month ago wasn't great. But they've since shipped a number of improvements and new features which has made the experience much better. Especially in bigger group chats like TSB.

It's a relative new project as I understand it, and is being actively developed, so I'm doing what I can to use and provide feedback (one of main devs is in the TSB chat).