Former Internet Explorer SE here: it’s not the coupling with Windows that makes it impossible (MSHTML is actually really self-contained). The main reason Micros

Former Internet Explorer SE here: it’s not the coupling with Windows that makes it impossible (MSHTML is actually really self-contained). The main reason Microsoft doesn’t open-source legacy code is because there a huge chunks of licensed third-party source code that cannot be publicly disclosed. While those portions could be stripped-out, it would be a mammoth task to go through the source code history and identify what belongs to who and stub it out if necessary (let alone replace it with first-party code). Whereas MS’ new projects (like .NET Core) were made open-source from the start and made in the open (Cathedral and the Bazaar) - so there’s no mean ol’ lawyers from LCA to stop people having fun.