Yes, the ARB file is a renamed zip file, as are any zap packs you may be using. As for the database, at one time it was a microsoft jet engine database. I seem to remember that they had to change it for performance reasons, but I can't remember what it was changed to, or if it was in fact changed. I just remember there were some issues with it.
I don't want anything on the Alibre servers, it takes way too long to open repositories as it is.
I'll just keep transporting my 1.2GB repository as an arb file. I'm using an old 6gb laptop drive in a USB enclosure, so there's still plenty of room to grow.
I wish they had a "Pack and Go" feature like Inventor - regardless of where parts are stored, the pack and go will pull them all together for the express purpose of relocating a model for local usage, but will also copy them all back to their original paths on the first computer. And to help what you were lamenting earlier - it takes every file that is in the project's "project file", including drawings, notes, etc.