@hadley Yes, it is also on CRAN now: http://cran.r-project.org/web/packages/rversions/index.html This queries the SVN, so it is not super fast.
I also have a web service, which just serves static data in JSON, it is updated after each R release:
You mean for not using my web service in the R package?
The R package was before and it is used to update the web service. I made the web service after, because I needed the current version without R, in https://github.com/metacran/r-builder, to check which version of R to install.
But I could use the web service in the R package by default, obviously. I am not sure if that's better or not.