LDAP: ultrapossum-server or slapd?

[Gezim Hoxha <gezimetc@shaw.ca>]

Hi all :)

I'm completely new to LDAP and the whole directory services thing.

What I want to do is have evolution calendar (for example) and
egroupware calendar synchronize automatically. So, I heard that I could
allow LDAP to be the storage system (is that term correct?). However,
the problem is choice (darned choice :)) because in the repos there is
the slapd and ultrapossum-server. They both seem to do the same job. 

So, my question is, which one is better, what are the differences
between slapd and ultrapossum-server?

Thanks alot.
-Gezim