Apologies if this has already been answered.

Sage (icebreaker) has +1 STR for each unused MU the runner has. Does this include MU that can only be used for specific purposes, such as Memstrips, or Deep Red?

Yup, I believe it should be treated in the same way was Overmind. So any unused MU counts even if it is for specific programs (such as deep red).

Many thanks.