OPush stands for OBM Push. It is an implementation of the Exchange ActiveSync server protocol. This protocol will allow complete synchronisation of the iPhone with OBM groupware servers.

What's in progress / not working

Other implementations of the ActiveSync protocol exists as free software:

• ZPush (I did not use their code as I wanted a Java solution, and most of the libs I needed to use were java ones)

Most other implementations are not free (as in speech and as in beer):

• Scalix ActiveSync
• Zimbra Mobile

If I wanted a non-free implementation, I would pick Exchange 2k7.