Earlier quoted context omitted.
If there’s no copyright, there’s no closed source. You get their code, decompile/disassemble and reuse as you see fit. You might argue that doesn't help much if they never distribute that code (only runs on their servers). Here’s the inconvenient truth: GPL already allows that. Anyone can take a GPL codebase, do any modifications they want, run it forever, and never contribute back. You’d need AGPL to forbid that. GP…
Here’s the convenient truth: GPL doesnt allow distributing the binary without distributing the code. Next one?
GNU Bash is GPL. You can run Bash (and many other Linux commands) in Windows through Windows Subsystem for Linux. In fact, WSL is a nice example of Microsoft doing embrace & extend.
The challenge: find the Microsoft's published code for Bash.