It violates EULA because it hacks your system. msstyle skins can be converted with SkinStudio to WindowBlinds skins.
That is the greatest advantage of WindowBlinds, can use skins made for WB and all the msstyle skins out there by converting them. WB is more advanced than msstyle, much more of the GUI is skinned. StyleXP can only use msstyle, WB skins can't be converted to msstyle.