After reading a little more about iCalendar, I stumbled across a nice summary of the different pieces needed for an implimentation. The summary RFC 3283 contextualizes the various pieces like this:
The relationship between calendaring protocols is similar to that between e-mail protocols. In those terms, iCalendar is analogous to RFC 2822 [Internet Message Format], iTIP and
iMIP are analogous to the Simple Mail Transfer Protocol (SMTP), and CAP is analogous to the Post Office Protocol (POP) or Internet Message Access Protocol (IMAP).
[CAP] seems to specify the granularity of access control needed to support iCalendar functions, so maybe that is where to look for ideas on the permissions required.
Things not addressed by the RFCs are user administration and user notification, but OpenACS already has this partially covered.
It is too bad that a new important service like calendaring has been shoehorned into the old and rusty email infrastructure. Apparently an important consideration is to provide a message format that is cut-and-paste'able on the deficient windows platform. OTOH, everyone knows the limitations of email and email software. Having some kind of MIME module for AOLserver would help out quite a lot.
