An updated internet-draft is available from the IETF.
Abstract: «The Calendar Access Protocol (CAP) is an Internet protocol described in this memo that permits a Calendar User (CU) to utilize a Calendar User Agent (CUA) to access an [iCAL] based Calendar Store (CS). At the time of this writing there are three vendors implementing CAP. It has already been determined that some changes are needed. In order to get implementation experience the participants felt that CAP needed to be released so that many years of work could be preserved. Many properties in CAP can be used by other iCalendar protocols and have had many years of debate.»