WordPress MU

Can I change my WPMU domain?

I've installed it in http://example.com/wpmu

Can I change it, without a complete reinstall, to http://example.org/wpmu?

My experience has been that I can make example.org/wpmu point to example.com/wpmu, but the WPMU site comes up identifying itself as being at example.com/wpmu.

The .org site is my organization's real URL and the .com site was one I set up to develop a new WPMU-based website.

Yes you can, you need to go through the database and change all the example.com references to example.org. I know that there is a utility someone has written to allow you do to this quite easily.