On 31 May 1996, id Software released the game Quake, which became a huge success. In 1999, the sourcecode for Quake was released under the terms of the GNU General Public License. Thus peolple could improve the engine and use the engine to create their own games. Soon after the source release, the QuakeForge project was startet to create a cross-platform engine that would appeal to many people. But having only a GPLed engine but non-free data files was unsatisfiyng so the QuakeForge team also startet Open Quartz.
Though being abandoned for many years, the project is going again thanks to new and devoted developers. But your help is still appreciated, there is a lot to do :-)

Why is having a free engine and non-free data so unsatisfying? Quake can still be easily aquired from the id Store and a Shareware Version is also available.
Yeah, that's true. Quake is a great game and we encourage everyone to buy it. Combined with up-to-date engines like Darkplaces, QuakeForge and Tenebrae it's still a great experience. The reasons why OpenQuartz is developed lie not with the availability of Quake nor is Quake a bad game. It's just that both a free engine and a free data set result in a lot more options and possibilities for developers and the end-user. It's for example not possible to ship Quake with any free Linux distribution like Debian. But you can do that with OpenQuartz. Also, when you want to create an own game using one of the advanced Quake engines, you have to recreate everything from scratch. With OpenQuartz, you have a lot of free content already availabe which means a lot less work. Also, creating standalone games from existing Quake Mods is now easily possible thanks to Open Quartz..