Wineskin is a tool for anyone to use... it supports building your own Wineskin Engines (Wine, X11, and other supporting libraries) from Wine source code. While standard engines use completely unmodified Wine source... whoever has made that Bully wrapper may have customized Wine source and made a special engine for it. You'd have to contact whoever made the wrapper, and see if they used a stock Wine build or not... its not something I'd have any knowledge of. I simply try to make Wineskin a good tool with tons of customization options to get programs working.
