djl is right regarding TivoWeb modules. In fact, I think hackman may be the only non-standard module that plays well with TWP 2.1, though there may be others I don't know about.TWP 2.1 won't load older modules without modification - the code is substantially different. It comes with quite a few built-in, though.
But other hacks, such as mfs_ftp, autospace, endpad, etc. are totally independent of TWP and work just fine. dvrpedia is a good source of information about other hacks and TiVo hacking in general.