mpp.terrium.net (MPT) is a clone of ourworldofpixels.com/piano (OWOPP/WOPP), which is a clone of www.multiplayerpiano.com (MPP). It was started because OWOPP's websocket server stopped being hosted, and there were no other active clones left.
The client files are hosted by GitHub Pages (from this repository) and the websocket server is hosted on the ts.terrium.net server, which is an extra VPS that Eric gave me to play with. (you could say this is sponsored by Terrium, so check it out)
Feel free to fork this repository and add your modifications. After you commit, your fork will also be hosted by GitHub Pages so you can run your client at https://your_name.github.io/repository_name. When you're ready, open a pull request to merge your contributions to this repository. If everyone were to contribute their modifications, this could become the ultimate community edition of MPP!