Metaswarm is a work-in-progress public domain bittorrent client written in Scala with Akka.
In the current state, it kinda sort of downloads (but not uploads) if you edit the source to specify the torrent file. A lot of the libraries used are now obsolete and have no version for Scala 2.13 or Scala 3. It is unclear if I will continue to work on this project.
I suppose it has served its purpose in making me understand the BitTorrent protocol inside and out.