Syncplay synchronises the position and play state of multiple media players so that the viewers can watch the same thing at the same time. This means that when one person pauses/unpauses playback or seeks (jumps position) within their mediaplayer then this will be replicated across all media players connected to the same server and in the same 'room' (viewing session). When a new person joins they will also be synchronised.
Download videos/channels/playlists from YouTube and many other sites
Tartube is a GUI front-end for youtube-dl, yt-dlp and other compatible video downloaders.
It is written in Python 3 / Gtk 3 and runs on MS Windows, Linux, BSD and MacOS.
Mediarelayer is a simple proxy server relaying/mirroring streaming media. It can import ASF-encapsulated streams from Windows Media Encoder, VLC mediaplayer, etc.