Project: https://github.com/hhannine/Superpaper
Why: replacement for HydraPaper
Open Source?: it uses the MIT License https://github.com/hhannine/Superpaper/blob/master/LICENSE
Link for the releases with Tarball: https://github.com/hhannine/Superpaper/releases
I think it's a better than HydraPaper and a good replacement.