RXPY is available for Python 2.6+. It will soon support 3+ too.
The source is more likely to be up-to-date (and consistent with the web documentation) than the current release. I am not making regular releases until the project is a little more mature.
However, the 0.0.0 release does work correctly as a regexp engine.
Distribute and setuptools are very similar, and either will install RXPY on Python 2.6. However, I recommend using distribute since it will also work with Python 3 (when RXPY runs there) and appears to be better supported.
That’s it. There is no need to download anything beforehand; easy_install will do all the work.