I know that these guys also use SourceGuardian - there are three different encoding schemes that they use (Zend, Ioncube and SourceGuardian) and i was able to install the SourceGuardian version with no problem for one of my clients. I think it depends upon the server set up - if safe mode is on, then you need to be able to edit the php.ini file.
I spoke with the guys at sourceguardian for a little bit of help and even though it is not their application that i was asking help on they really helped us out to get us running
John