Paul wrote..
What are the rules about carying passengers in the "Other" experimental
catgories?

As I understand it, one may give a ride in an Experimental two-place sailplane,
but he can't charge for it. A bigger problem is that instruction is not allowed
to be given in a two-place sailplane.

Are these rules ever enforced?

Probably not, until you have an accident and then your insurance company will
be quite interested in your activities.
JJ Sinclair