The current version is 2.4.2 available from Launchpad as you noted. All published versions as well as the upcoming 2.4.3 are available from GitHub
https://github.com/mlhim/specs
The history is that we began in 2009 with 1.x to be compatible with openEHR. However, the more we worked on it the more we realized what was unnecessary so we removed it.
There is a site Healthcare Knowledge Component Repository
http://hkcr.net/ that has example CCDs from various reference model versions. Though this site hasn't been kept up to date since we published the CCD-Gen (CCD Generator) and the various academic projects have gotten underway. At one point we had all of ICD-10 modeled on the site. Since they were on RM 2.4.0 we removed them. We are currently modelling all of the NCI Common Data Elements (CDEs) and CRFs. The CCD-Gen allows us to create reusable complexTypes (we call Pluggable Complex Types or PCTs) for the CDE models and full CCDs as the CRFs. See:
https://wiki.nci.nih.gov/display/caDSR/CDE+Browser