Welcome to the hgsubversion project. The goal of the project is to create a fully-featured Subversion client that works as an extension to Mercurial suitable for inclusion in the stock Mercurial distribution.
See Design for some thoughts on the design of hgsubversion. The developers can be reached through the mailing list or [[irc://irc.freenode.net/#hgsubversion|#hgsubversion]] & [[irc://irc.freenode.net/#mercurial|#mercurial]] on FreeNode. There's a list of test repositories that we use to try and verify how well the conversion works.