There is PDF documentation here, which may be slightly more useful that this page - Thanks Serafeim!
The easy option, recently available, is to download the daily builds, links to which can be found at http://wiki.alu.org:80/Slim-Vim-Repos.
If you prefer to build from fresh sources (and sources are always tastier when fresh), the following will be helpful.
First you need darcs, as that's what's being used for the repositories. Binaries (and sources) can be found at