Back in 2010 the nightly builds for RawTherepee were to hard to maintain, so we stopped them. But since then a lot has been changed and new packages have just been published on launchpad. At the moment there are some dependency problems with Ubuntu 10.04, 10.10 and 11.04. But we will try to backport some of the packages at least for Ubuntu 10.04 LTS.
For more information have a look at the service page.