Hello Webmister,
GroupID 5 will work with Exchange 2007 Service Pack 2 as long as you do not update the schema while installing Service Pack 2.
If schema is upgraded for Exchange 2007 Service Pack 2, GroupID 5 will not work with it. It also does not support Exchange 2010 at this time.
However, there is a new version of GroupID named GroupID 5.5 which is due by March/April this year. GroupID 5.5 will support both Exchange 2007 SP2 (with updated schema) and Exchange 2010.