The ioDoom3 project comes from the creators of ioquake3, the code-base that was formed when id Software had released the Quake 3 (id Tech 3) source-code a half-decade ago. The ioquake3 engine is what's used by OpenArena, World of Padman, Urban Terror, and many other open-source games. The ioquake3 developers are now looking to do the same for this more impressive game engine via the ioDoom3 effort.
Right now the infrastructure is still being setup and developers are only beginning to dabble with this code that was just published hours ago. The project web-site for ioDoom3 will be ioDoom3.org.
Best of luck to this project and hopefully there will be some interesting open-source projects taking advantage of the Doom 3 / id Tech 4 engine source-code. I've already fetched it and am beginning to look into new performance tests or other ways to benchmark this newer id Software code.