Complex sentence: First posted to comp.sources.games in 1987, it is notable as one of the first multiplayer games to be released for the X Window System, and was for several years the only turn-based graphical wargame available on Unix/X systems.
Split into simpler sentences: First posted to comp.sources.games in 1987, it is notable as one of the first multi-player games to be released for the X Window System. It was for several years the only turn-based graphical war game available on Unix/X systems.