I'm interesteing, why someone not reverse engineer old windows 3.1?
In theory, win 3.1 have no kernel(because kernel is dos), it's simply window manager(such as x window on unix), so why i can't reverse engineer it's and modify?
Someone should have reversed win3.1 when they needed it... they are probably retired now.
Others reimplemented Win3.1 API (Win16) in the WINE project using published API references rather than reverse engineering it (to avoid legal issues).
Early DOS source code is released a while ago.
You can reverse anything you want. You may however not be able to release any of your findings.