Hi Ertan, we are in the process of moving all of the jBPM Designer code to the jBPM github repository. This will be done either alongside the jBPM 5.2 release or shortly after. At this point all of the development will be done there. As far as support goes, I have heard that the jBPM Designer will be a supported feature in JBoss BRMS 5.3. For concrete info on professional support, please ask the Red Hat Sales guys as they should be able to get you more specific info.
Hope this helps.