OP said source available was acceptable. not even asking for compiler access which is also widely available.
Windows has always been more than modular enough for any repurposing and there were licenses that were not tied to specific hardware so you could use them even today.
Which is to say no one is stopping you from building a COPILOT.VBX for VisualBasic 3.0.
Yes but it could not be legally used by anything.
OP said source available was acceptable. not even asking for compiler access which is also widely available.
Windows has always been more than modular enough for any repurposing and there were licenses that were not tied to specific hardware so you could use them even today.
Which is to say no one is stopping you from building a COPILOT.VBX for VisualBasic 3.0.