Microsoft disabled the AARD code for the final release of Windows 3.1, but did not remove it so it could be later reactivated by the change of a single byte.
DR DOS publisher Digital Research released a patch named "business update" in 1992 to bypass the AARD code.
I don't take Wikipedia as gospel, but that doesn't say what happened with earlier versions of Windows. And regardless, how did DR-DOS sue them if they weren't affected?
the check for dr-dos didn't exist except in that beta version of Windows. there were no media reports of dr-dos problems with windows before then. according to the wikipedia entry, the code was disabled but still shipped in windows.
I've never heard that and IIRC, DR-DOS's owners sued successfully (or DoJ sued successfully). People certainly saw the errors.