Hi Gerry,
Chris is exactly right. Appeon's releases of PowerBuilder are separate from SAP's releases even though the code base is quite similar for our first release. Of course, because Appeon's release will be regularly adding new features then over time Appeon's release will be able to do much more than SAP's version 12.6. Also, customers may want to upgrade simply to be on a supported version.
If you haven't seen our PB roadmap I encourage you to watch the Webinar recording: http://www.appeon.com/recordings
Anyway, to answer your question about licensing, there will be a separate purchase but we are now working on figuring out an attractive pricing and promotion for existing PB customers such that it would be attractive to upgrade to our release even if you are still on active maintenance subscription with SAP.
Details about licensing/pricing will be announced in the near future - stay tuned!
Best regards,
Armeen Mazda
CEO, Appeon