UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
KJams - KJams is a free app offering the largest selection of karaoke tracks in one easy-to-use place.
OpenKJ - Open source cross platform karaoke hosting software
Karaoke Mugen - Video & Movies and Audio & Music
Siglos Karaoke Professional - Siglos Karaoke Professional is a professional karaoke player who can make your party become more exciting.
QMIDI V2.0 - QMIDI is an open source karaoke player for Windows, Mac OS, and Linux.