It's like they've confused the valid idea of an open source programmer being tainted by looking proprietary source code, with the ridiculous idea that a user interface designer would be tainted by looking at or using a proprietary user interface.

Some aspects of Photoshop's user interface are patented, but it's much safer and wiser to LOOK at them and be aware of them and read the patents, so you're consciously aware of what not to do accidentally, and able to work around them.