text: id Software, the original developers of Doom, also continued to release their products for Linux. Their game Quake was ported to Linux via X11 in 1996, once again by Dave D. Taylor working in his free time. An SVGALib version was also later produced by Greg Alexander in 1997 using recently leaked source code, but was later mainlined by id. Later id products continued to be ported by Zoid Kirsch and Timothee Besset, a practice that continued until the studio's acquisition by ZeniMax Media in 2009. The ports of Quake and Quake II were released physically by Macmillan Computer Publishing USA, while Quake III was released for Linux by Loki Software. Red Hat had previously passed on publishing Quake for Linux, since it was not open-source at the time.
  In 1991 DUX Software contracted Don Hopkins to port SimCity to Unix, which he later ported to Linux and eventually released as open source for the OLPC XO Laptop. Other early commercial Linux games included Hopkins FBI, an adventure game released in 1998 by MP Entertainment, and Inner Worlds in 1996, which was released for and developed on Linux. In 1998, two programmers from Origin ported Ultima Online to Linux. The UNIX Book of Games, a 1996 publication by Janice Winsor, described various games with an accompanying CD-ROM containing executables and source code for Linux and SCO Unix.