OpenGroupware.org is unique in the OpenSource groupware server space in its flexibility. Being organized as a set of reusable components, OGo is more a Groupware Construction Kit for building customized team collaboration applications than a server hardcoded for a particular application.
Add to that the wide range of supported APIs and protocols and you know why resistence is obsolete ;-)
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Development on various parts or extensions of OGo is organized in "projects" - a project usually has a project homepage and an associated mailing list where development is coordinated.