WindowShade was amaaaazing. There was something that - for a while, was an OSX equivalent…I want to say ‘ShapeShifter’(?) - but it only worked for versions from like 10.2-10.4.
There was a utility called "WindowShade X" which (messily) hacked the functionality back into early versions of Mac OS X. This developer's utilities had a nasty habit of breaking with every OS update, though, sometimes even making the machine fail to boot, so it probably comes as no surprise that it's no longer available.
The same developers also had a UI skinning utility called ShapeShifter, which is probably what you're getting WindowShade X confused with.
You might be thinking of SheepShaver, a Mac emulator for BeOS and Linux. Its name is a play on the name ShapeShifter, an earlier emulator by the same develope, which was an Apple II emulator for the Amiga.
