That's the reincarnation of the dead now Maven Repository Manager Feature Matrix and it picks up exactly where the Codehaus page left.
This repo is administrated by all the commiters of the Codehaus page (@olamy, @brianf and @jbaruch), representing all the products in the matrix. They make sure this comparison remains up to date and unbiased.
PRs are welcome as well, feel free to edit the docs/content/_index.md file, TravisCI will pick up the changes and generate the static HTML for it.