I totally agree. AlienSkin needs to fix this. On the SDK issue, several toolkits are free to use by the public to develop in C++, VB, etc.. Java SDK, .NET Framework, etc. That anyone can use freely.
Here's what I got from AlienSkin today...
I am sorry that you are unable to install Eye Candy 6 into Corel PhotoPaint x6. Having to make the decision to drop Corel support was not something we took lightly. It was a difficult decision for us. The truth of the matter is we are a small software company and Corel kept changing things in their programs that required full rewrites of our software in order to be compatible. This is something that was just not possible for us to do. The fact that this has left you stranded bothers me, but there isn't much I can do.
I have run several tests up to this point. I installed both 32 and 64bit versions of Corel PhotoPaint x6. As you have found, in the 64bit version, everything but Eye Candy 6 shows up. However in the 32bit version, everything shows up even Eye Candy 6. How much memory(RAM) does your computer have in it?