It is also my understanding that Zope, when it is capable of using an SQL database as its primary storage, will not be tied to any specific database type.
This is true. I've been developing against Interbase as of yesterday, but it's pretty trivial to make a RelationalStorage work against any SQL database (if it supports transactions). I started with MySQL (because I already had it on my machine), but it's almost impossible to guarantee data integrity using it. However, Oracle, Interbase, Postgres, Sybase, etc. should handle it fine. Those interested may want to check out http://www.zope.org/Members/jim/ZODB/RelationalStorage. There's a design there and a (very, very broken) implementation (in the off chance that you happen to get it actually running, do NOT try to use it to actually run Zope on an actual honest-to-god server). I could use any comments folks have to offer.