Copyright: etterna
Excerpt grabbed from the Etterna GitHub readme:
Etterna is a cross-platform rhythm game similar to Dance Dance Revolution. It started as a fork of StepMania 5 (v5.0.12), with a focus on keyboard players. Over time, Etterna evolved into its own game, with in-game multiplayer, the online scoreboard Etterna Online, and a community of over 4,000 players.