I have looked through Adobe resources for panels and CS5 extensions. I have sent e-mails to Adobe engineers. Here's what I've learned.
There are some incompatibilities with the CSXS library that panels use and Macs. In theory, the technology is platform-independent. I am not the only one to find that the same Action Script code that works for PCs does not always work for Macs. Often it does, but not always. There have been support messages posted about this and no solution from Adobe so far. In fact, I haven't found where Adobe engineers even acknowledge the issue. With respect to my e-mails, one engineer punted. Two others did not even respond. Given that Adobe engineersusually respond quickly, this s very curious.
I face a decision, and I'll ask for community help on this point! Do I go forward with porting the exisitng panels to work under Windows for now and then hope that Adobe fixes the Mac issues with CSXS in a Photoshop update?
I don't want to ignore Mac users. On the other hand, if I can help the Windows users while I wait for a solution for Mac users, that would help a lot of people.
The other solution is to obtain Adobe Creative Suite Extension Builder. It uses panels, but it is a different technology from the CSXS panels from CS4 (and that I am porting to CS5). Adobe appears to care now about CS Extensions, not older technologies.
The problem there, is the cost. You have to be a subscriber to one of Adobe's developer support plans to obtain Adobe Creative Suite Extension Builder.
That's $500 per year at a minimum. Plus, the panels have to be digitally signed or users will get a noxious warning when they install them. That's another expense of around $200 a year. That's all too cost prohibitive for me at this point, since I give away all the panels.
Adobe used to make resources like the Adobe Creative Suite Extension Builder without charge to developers who agreed not to sell their panels, scripts, plug-ins, etc. That's how I obtained the SDK in the past. With the change to CS Extensions, it's a pay only option.