I would assume you can run WebEx because ReactOS says they have 100% binary compatibility with Windows. What you’d need to run any Windows program is a way to

I would assume you can run WebEx because ReactOS says they have 100% binary compatibility with Windows. What you’d need to run any Windows program is a way to parse the PE executable format, load it into memory, and emulate or simulate W32 api calls. I’m sure there are other steps but I can’t think of many more off the top of my head.