Earlier quoted context omitted.
No upside for the company? Do you not see all the people who are delighted to be able to browse the code?
No commercial upside for sure. Just some extra reputation points among a very niche group and maybe some happy employees.
Frankly, there should be regulations guaranteeing source code release after a few decades, and that all code, including third party code, is released from copyright protection. In return, companies should be granted legal protection from any potential legal consequences. It was over 30 years ago. The idea that somebody should be able to sue Microsoft for copying code or a third party can sue them for releasing it or that they should in any way be punished for unsavory language used THIRTY years ago is clearly utter insanity.