Larry Augustin, a venture capitalist and early open-source entrepreneur, made a really good point via e-mail in reference to my post about VMware violating the GPL. A range of people in the open-source community has been pointing the finger at VMware for allegedly creating derivative works of Linux in its ESX virtualization technology without contributing those changes back.
Larry's suggestion? If VMware is violating the GPL, so are a lot of others...with Linus Torvalds' (apparent) express permission. With Augustin's permission, here is part of his e-mail to me:
This is a longstanding general problem. It is not a VMare-specific problem. Are binary Linux kernel modules allowed? The answer is unclear. This question has a long history going back to the first binary kernel module, Transarc AFS. In an e-mail to the developer Linus explicitly allowed that module. That e-mail is the basis for the "loadable module exception" often quoted by many people.
But it's not as simple as that. The way in which the loadable module interfaces to the kernel is potentially relevant to the question as well.
My understanding is that if VMWare is violating the GPL, then it's likely that so are all the other vendors that use binary modules in the Linux kernel.
As Augustin suggests, it's not quite that simple--Linus Torvalds has clarified the "loadable module exception"--and it's not clear to me on which side of the line VMware would fall.
Such modules negate the openness, stability, flexibility, and maintainability of the Linux development model and shut their users off from the expertise of the Linux community. Vendors that provide closed-source kernel modules force their customers to give up key Linux advantages or choose new vendors.
This appears to be a risk VMware is willing to take. But given the increasing competition it's feeling from open-source virtualization, perhaps it should reconsider.
In other words, VMware may not be violating the GPL but could be bent on violating community and common sense.