Has this sort of thing been argued in court as an ADA issue? I could understand why using Linux might be considered legally a "choice", but if there's better ADA compliant tooling in Linux over windows, then a legal argument might just exist..
It shouldn't be allowed to ban web access from all free operating systems ;)
"You are using a non-free Operation System and thus signing away you fundamental rightsas a user. Please use a free Operationsystem like GNU/Linux to access this website."