Oracle, and before them, Hyperion have moved away from that. In the days of Arbor, when rocks were soft, ports-based licensing was the norm. However, if you look at the way a lot of the tools are architected (Planning is the primary one) connections to Essbase occur on one or maybe two ports. Hence the move to naming users.
IANAL, but my understanding is what you stated -- the named user approach requires you to buy a license for each user you set up in Essbase.
I *think* Oracle has a licensing group. Your friendly neighborhood Oracle sales rep should be able to put you in touch with whoever that is.