Hi… I’ll try to address all your points…
Simple Server won’t run – what do you mean by “does not start at all”? Nothing happens when you double click it in the Finder? (if that’s the case, are you sure you’re running MacOS X 10.6?)
“how do you get image or video to server.” – Simple Server is just a demo, it only plays the Syphon logo, it’s not very useful, so you can probably ignore it anyway. The server needs to be made inside the application that’s sending the images.
So can I use any app (Alchemy, Photoshop) that puts out a image/video through GPU or only apps that are *implemented* do it among each other?
No, the application needs to support Syphon, either natively (because the developer has integrated Syphon), or through a plugin or similar extension, like Quartz Composer, FreeFrame, etc.
I don’t know much about Alchemy, though it looks like something it would be great to get working with Syphon. I’d suggest asking on the Alchemy forum – if anyone there is interested in working on Syphon support we’d be happy to lend a hand.