The last update in the official IVAN CVS is from 2006/09/22. I don't think it was officially named 0.60, I just call it CVS for a lack of better name. IVAN 3D is based on it, and only adds interface options, so balance and gameplay is the same except that valdemar abundance is fixed. I don't have any links, but if somebody does not want IVAN 3D then I can recompile it.
edit: Oh, you meant continuing IVAN development unofficially? I thought you meant the CVS version, which was called 0.60 by lampshade, I think.