From Rigs of Rods Wiki
Download the latest version here
Although you can find packages for various distributions here, it is recommended that you build RoR yourself since the packages get outdated real quick.
We got some scripts ready that do the job for you:
If your distributions isn't listed above, follow this link for general building instructions: Compiling_Sources_under_Linux
Unfortunately, due to lack of MAC coders, there is no up to date port of the latest version available. Below are some old versions:
You can find all Mac releases on SourceForge.
Overview / Readme / FAQ
You can find more information about the latest release here: Gaggenau
Many questions are answered on the wiki, have a look aroung: Main Page
Rigs of Rods has been open source under the GPL v3 license since 2009, meaning it is both free as in freedom (you can modify it) and as in beer (it doesn't cost you anything).
If you are interested in Rigs of Rods' history check out the museum here