That's pretty much it. Cosmopolitan Libc is the simplest project that could have happened decades ago. Anyone could have built it. There's never been a technical reason why an x86 binary can't run on all x86 operating systems. It's just that traditionally only operating systems publish C libraries, and they have no incentive to spend money supporting their competitors. So it's the kind of project that could only happen if it was done by an indie developer just trying to have fun.
The only programming environment I used to build this was Emacs on Linux. The rest was simply researching the magic numbers needed to use the binary interface of each system. I figured life's too short to be pulling my hair out with MSVC/Xcode warnings.
Does cosmolibc allow you to run on bare metal? If so, I've got an old project in mind that you may have just made happen, and I'm very very excited to know!
I recommend using InfoZIP on the Linux or Mac command line. For example, to list the files that are in your .com executables you can run a command like: