jappix is a fine piece of xmpp (jabber) based community building software.
Sadly, its installer needs php-mbstring (for SLES 11 SP2, this is php5-mbstring or php53-mbstring depending on your php choice). Sadly, it hides any error messages before requiring this crucial library. You will never know until you investigate closely.

Or as some person on the web paraphrased in German: was meinst du mit testsuite?
Software should not behave that way. Test suites and installers like jappix’ setup.php should know how to handle missing dependencies and show them to users.

Debian is not affected. By luck or purpose, debian ships mbstring with the basic php package.