Steve,
We had in fact worked this very issue both onlist and offlist during the OCSP drafting stage. That work led to the consensus view of an OCSP Authorized Responder as defined by Section 4.2.2.2 of RFC 2560 (cf. my note the list on 06 March). So it seems we already have a consensus-based notion of what to call a non-CA OCSP entity--at least from a standards perspective.
Just trying to save the WG some cycles.