"The ZFS issue is just an example of how difficult could be to develop kernel modules without giving IP away."
That shows a complete misunderstanding of the situation. Firstly virtually no "applications" need any kernel modules, typically that is for special hardware and things like file systems. Secondly you can develop a kernel module and make it available as a binary blob to be added to someone's Linux system if you want - after all that is what Nvidia, etc, do for graphics drivers. The current argument is about a distributing the GPL Linux kernel with a pre-compiled non-GPL driver and if that makes it "distributing a derivative" of the kernel (which seems a bit bizarre argument).
The lack of specialist applications for anything other than Windows is simply a historical artefact of 90+% of desktop computers being Windows based, why would you bother with the other 10%? However, if a lot of folk move off Windows due to this, or other reasons, then software developers may start to see the value in using cross-platform tools (like Qt and similar) so they are not tied to MS uncertain future roadmap.
Or just run stuff in a Win7 VM without email/web/external Internet access and forget about the future patching (or lack of) for the OS.