rlparker recommends Lyceum as being easier to install and manage.
I installed mu for a while but decided to reimplement in Lyceum. That project is on the back-burner for me so I don't have an experience report on it.
Mu was pretty easy, though. I had some real problems with spammers creating new blogs - I had to leave registration open relatively open because of the nature of the project.
There are a lot of subtleties in how the two implementations treat plugins, so it's worth thinking about.
If you're just going to have three blogs, I'd think about having them be separate full installs. Why do you want to use Mu instead?
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