I think the biggest thing that came out of that anti-trust case is the publishing of specs for various file formats and protocols used by Microsoft software.
And the duplication of... about two dozen string routines, from what I've been able to find.
The actual rendering engine was left to Windows (and to anyone who was using it, like AOL), the shell was left to IE to continue wrapping around it, and a few more things.
This mostly talks about APIs, and only briefly mentions protocols.
I don't know about the specifics of what is legally required vs what the Microsoft legal team decided to do to avoid further scrutiny. But the fact is that there's a lot of docs that were published in the aftermath of that ruling:
The actual rendering engine was left to Windows (and to anyone who was using it, like AOL), the shell was left to IE to continue wrapping around it, and a few more things.