Is there some basis for it being haram? You can have strong core beliefs that don’t have to be rooted in religion, even if it wasn’t haram if you believe that you should avoid proprietary software then do so, it doesn’t really matter if Islam doesn’t care. Religious interpretations vary so wildly anyway, focus on how you interpret it.

Calling something the “gravest crime” seems kind of strange. So genocide is better? Mass rape? Why compare?