I'm not sure that I really understand the license changes. Here's what the email from Jelsoft said:
Beginning today, we are introducing a new license structure. vBulletin is changing to a one-time owned license fee for each major point release. That means no more annual renewal fees. Once you purchase a major point version, you’ll receive maintenance, security and minor point releases for the life of 4.x.
You have the option to keep your current active license until it expires (according to the 12 month term and conditions). For the remainder of your active license, you will continue to receive support and have access to forum software updates, including vBulletin 4.0 Forums. Once your license expires you will only be able to access the 4 Series software updates by switching to the new one-time owned license. For more information, visit the vBulletin FAQ.
This sounds like an improvement to me. It sounds more like the license structure they had prior to the Jelsoft acquisition.