Hi again !
I focused on the Mac world for two main reasons. First of all, I am a Mac user and know the Mac world in more detail than the Windows world. Then, Apple has recently worked very closely with the Open Source community when developing Mac OS X, probably more than Microsoft when developing Windows. I am sure there are many interesting articles to write on the relationship between operating systems in general and the Open Source world and I always read such pieces with the greatest interest. This was not my point here, though.
I am afraid that your reaction is mainly based on an unfortunate misapprehension of the goal of this page. As I stated in one of my previous blogs ( The power of the Mac community ), we Mac users are always glad to discuss computing issues with other OS users. I am in now way trying to start an "operating system war" that wouldn't lead to any positive results.
What I am trying to say about mixing proprietary and commercial solutions is pretty simple. Would you work with the proprietary format X, that is only read by application X, you are locked into a solution. When I use Keynote, the resulting file can be read by other applications. When I use iTunes to create an AAC file, I am not dependent from the application I use and remain free to switch if I wanted to since many applications can read the standard AAC format -- even when the applications in themselves are not open source.
I do not think that Apple is helping the Open Source community "because the license requires them to". Indeed, although some licenses may require commercial users to give back the code they may have written, this not always the case -- far from it. Furthermore, in most cases, Apple works closely with the development teams and this serves as the basis for a true cooperation -- much more than a law-induced exchange of code.
I cannot comment on Adobe's policy and will let them reply. About Apple, I can only invite you to have a closer look at the Apple Developer Connection site where you will find more links to answer your questions. Would you not trust the ADC -- for any reason --, you can always browse the Open Source sites by yourself -- FreeBSD, KDE, Apache...
I think that the Open Source community can benefit from any help -- as we all can. Kernel and servers are not to be neglected, even if there is a new focus on desktop applications.
I do not believe either that the Open Source community should stop developing an Open Source desktop -- as I already state in my blog : the creation of new projects always benefits everyone. I am simply saying that, nowadays, Mac OS X is my platform of choice as well as the platform of choice of many -- former or not -- UNIX, Windows and Linux users. Again, I do not think that this will "hurt Apple" either : every solution has its strengths and its place in the computing world.