fwiw: i could have sworn there was a 64 bit version of dopus on their build-server (back then). At least there used to be a v1 version (so that only the (address)pointers would have been affected).
In case not, making it 64 bit aware would be a problem for almost any piece of software and requires the painstaken process of reviewing/overhauling the code.
as ar as my recollection goes bszili, deadwood, miker (is that you?) and our russian friend (sorry forgot his name) used to work on (old) dopus.
DM2 would be fun to run as well of course