I require uploading an arbitrary copyrighted work to my site to login
The keyword that makes all the difference is "arbitrary".
Roblox can certainly require access to a complete copy of a copyrighted file in a windows installation (i.e. by requiring sending bytes from random offsets in it to their server, which could only be faked by having the whole file anyway)
Ironically, Microsoft offers the copyrighted files available in a Windows installation for free download, both in the form of complete ISOs and Windows Updates.
https://en.wikipedia.org/wiki/Sega_v._Accolade
https://en.wikipedia.org/wiki/Lexmark_International,_Inc._v.....
I require uploading an arbitrary copyrighted work to my site to login
The keyword that makes all the difference is "arbitrary".
Roblox can certainly require access to a complete copy of a copyrighted file in a windows installation (i.e. by requiring sending bytes from random offsets in it to their server, which could only be faked by having the whole file anyway)
Ironically, Microsoft offers the copyrighted files available in a Windows installation for free download, both in the form of complete ISOs and Windows Updates.