Customising a WPMU template will affect every blog using that theme, so I didn't expect this approach to be used in WPMU.
Then I found that, for example, http://wpmudevorg.wordpress.com/project/List-All, provides a function that can be called in WPMU (in this case to list all blogs).
I'm new to WPMU, and trying to understand how this works. How do I use such a function, but affect only a single blog? Do I have to add in conditional terms to the template, for example, so that the function's only called for the blog I want it used in?
I guess there must be a fairly standard work-around for this, but despite a few days searching over the hols, I haven't found a discussion. I'd really appreciate some pointers to what others do. Apologies if I'm missing something obvious.