It's true that ours doesn't look like the traditional BSD 3 or 4 clause licences - some people had already spotted that, but as it came from Berkeley we always just considered it to be a variant on the simplified BSD licence. The long and short of it was that lawyers said "no they're not the same", and we said "well it sure ain't MIT" and much discussion ensued.
The solution it seemed, was to try to get our licence recognised and approved by the Open Source Initiative. I originally tried to do it as an official BSD variant, but that wasn't accepted. I then resubmitted it as 'The PostgreSQL License" (yes, I know :-p), which was rejected as it wasn't a generic licence (OSI are trying to ensure that all new licences are resuable). Finally, I submitted it again with placeholders replacing the project name and copyright holder info, and nearly two months later, it's approved!
So there you have it ladies and gents. "The world's most advanced database with freely available source code" now actually is, officially, The world's most advanced Open Source database"!