The discipline of being posix compliant forced Linux to innovate across the defined boundary. I recall Chris Click's talk about JVM and its definition of garbag

The discipline of being posix compliant forced Linux to innovate across the defined boundary. I recall Chris Click's talk about JVM and its definition of garbage collection APIs, class libraries etc each enabled innovation to be done independently of one another. There is no such story for kernel-mode drivers. The problem was so dire with network card drivers at one time that there was a project that enabled windows drivers to work on Linus. Think about it - if Linux standardized on a stable external API, then there'd be no arguments about how to implement it. Linus kept talking about userland vs kernel, and did not address the issue Miguel talked about. Kernels need performant external interfaces too. Drawing a line around what is being innovated and changed will only help Linux the way posix did. On another tangent, when Microsoft made IE6 the stable browser platform, it gave a clear goal for Mozilla. It became a reference implementation, allowing Mozilla to emulate all the layout behaviors and eventually carving out a nice marketshare for itself.