Gilles explained very well the evolution from piece to another here, so I will cover the topic from more broad perspective and give some hints for further research.
From Bazaars and Research Labs to Closed Blobs and Market-marginalized Groups that I think are not that marginal at all
The key term to play with evolution is power. If you are dependent on an OS, for example in the form of security updates, you are dependent on the software-manufacturer and hence it has power over you. It can decide to stop publishing security updates or do any evil that its license allows it to do. If the OS is closed, the users must feel helpless because they cannot fix problems on their own, perhaps shown in hypocriticical feelings such as again the damn driver broken, XYZ's fault. In the latter discussion, you can s,OS,sofware,g and it does not really lose its meaning about power-relationship, clearly some thing being timeless.
I won't reinvent the damn wheel so please read about Bazaars, corporations and social-environmental-and-other problems below.
Start
Ending, Now and Still Evolving
- Amos Batto's essay explaining some reasons behind closing things (Internet Archieve article, cannot be found from Google easily)
- For visualizing the evolution, please, see the picture below from Wikipedia where things started from Bazaar (orange phase) and ended to red-green phase where things are still evolving or even chaotic.
The FOSS movement is not a marginal body, please, note that they do have their own things such as music (here or here)and more-and-more hardware (here). If your media says something else or nothing, they are ignoramuses.
Your questions have too many confusions to attack them easily, such as presupposition about hierarchy that ignores the idea about chaos and ambiguous terms such as Windows -- dev branch or branding? And the term from Unix in the title tastes too much appealing-to-populism-in-Unix-quesion-site. It is hard to say how /dev/null such as W. and other closed things evolved because we don't know them, except speculation! People who know cannot speak. The source is primary, the rest is secondary. Be sure which blindfolds, i.e. search engine, you use for this topic, many valuable articles are dumped with irrelevant information as the case with the above removed article. As a starting point, you could try some links offered above.