What do you want to know?

Is The Marvellous Suspender open source?

Yes. The code is publicly available on GitHub.

Is TMS compatible with Chromium browsers?

The primary distribution channel is the Chrome Web Store.
For compatible Chromium browsers, verify installation and supported policies case by case. Currently, we have users of Vivaldi (primarily), Brave, and Microsoft Edge who use The Marvellous Suspender on a daily basis.