I maintain an open-source application project, which I committed in a public GitHub repository. The source code I wrote is open-source (under MIT license) and owned by me, however it depends on a third-party library, for which the source code is proprietary of its providing company.
Of course I bought a copy of this library, however for practical reasons I want to create a private GitHub repository, on which I think commit this proprietary source code and link it as a sub-module in my public application project.
I performed a test to check if a thus created private sub-module may be accessed by anyone from my public application project, and it seems it's not the case, although the sub-module appears as a link, which is exactly what I wanted: an access to this sub-module for me exclusively, and no access for any person which just want to get my source code.
However is a such practical legal? I.e can I commit the proprietary source code of another company in a private repository I own, if this repository cannot be accessed by other persons than me?