UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
Karaoke Mugen - Video & Movies and Audio & Music
Walaoke - Walaoke is the app that makes it fun to sing karaoke anytime, anywhere.
OpenKJ - Open source cross platform karaoke hosting software
KaraokeParty.com - Sing karaoke online and get a score based on your performance.
Midica - MIDI and Karaoke player and file analyzer and interpreter for MidicaPL music programming language.