M$‘s priority is to draw new people on their products and make people upgrade to higher tiers. Existing users are none of their concern. There are business models who will put the product team to focus on existing users. One way is an open source product run by the users community, another way is product relying on the effect of word of mouth.
Sadly not under the cold war we are having right now.
You can view and contribute, so do all the help possible but you can’t modify/rebuild/release a different version. That is not open source, that is called open to volunteer.
Open hardware is not something sustainable. Hardware does not enjoy the benefit of open source software.
Open projects inside the 3D printing community might be possible but anything requires heavier R&D would not work.
Firefox is somehow struggling at picking up feedback from users and Safari is not open source.