Licensing
The Racer software is free, in the sense of freeware (for non-commercial users). While the source code of an older version is available, it is not under an open source license. The cars and tracks have various forms of license, but can all be downloaded for free.
Whilst one of the strengths of Racer is its open file format, perhaps one of its weaknesses is its closed-source stance and development team. The Racer community contributes to testing and suggesting features that should be added, but the development side of Racer is very much based on the amount of time the developers have to contribute towards it. This translates to infrequent updates of varying quality, but updates are often very feature-rich and inspire a new burst of energy into the development and modification of cars and tracks.
Read more about this topic: Racer (simulator)