that is not the problem.
the problem is that dreamhost runs php as a cgi, wich results in problems accessing the basic authentication info from php. z-push needs this to forward it to the imap backend.
with a few changes, it is however possible to get it working.
I use since a few days, and it works great.
if you need my code, please mail me at g e r t AT p a r i s i s dot b e