I commented to the blog, saying that it was incomplete to say "Red Hat and IBM are making their sources available to all those who receive their binaries under contract. That is the GPL." The blog responded, it's submitted for moderation - but I do not see my, or any other comments.
A simple search on "Linux GPL-2 license" yields "The Linux Kernel is provided under the terms of the GNU General Public License version 2 only", and on the gnu site, "Accompany it with the complete corresponding machine-readable source code [...or...] give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code". For brevity, I synopsized this in my comment.
I see too many articles saying that Red Hat only have to provide source code to its customers - and the blog only implies that - but the Linux license requires more. The community often takes the source code, compiles and matches the binaries. That is essential. Red Hat offers a service, support and warranty, but as the license says, you cannot just take the source code, you have to give it back too.
I had a contract where source code had been lost, until I found a printout, yellowed and wrinkled, showing self-modifying code to boot, and assembled that, finding a match to the binary, at which point I could produce a module that could be maintained in the future. That task would have been much more difficult without source code.
"I see too many articles saying that Red Hat only have to provide source code to its customers - and the blog only implies that - but the Linux license requires more."
The GPL only applies when there is distribution (either in source or binary form) of a work covered by it. And it only applies between the parties involved in that distribution transaction. The GPL doesn't mandate that a covered work be distributed. The combination of these three aspects is critical.
Red Hat only distributes RHEL to its customers (it isn't available for anonymous download), therefore the GPL only mandates that Red Hat provide corresponding source code to their customers. The GPL also mandates that Red Hat allow its customers to redistribute any received binaries or source to anyone. Red Hat is free to decide who can be a customer, and to refuse to distribute some future version/modification of a GPL'ed work to an existing customer.
The meaning of "all third parties" in the GPL is confusing, but it's important to understand that the two parties of the license are the original author of the code and a recipient. In this context, the third parties are anyone to whom the recipient later distributes the work. Not anyone random that happens to approach the recipient asking for distribution to happen.
The term "any third parties" means the recipient cannot violate the terms of the GPL upon redistribution, no matter who it is distributing to. For example, it cannot ask that "third party" to forfeit its rights to redistribute the work it received.
In summary:
1. Red Hat can refuse to distribute a GPL'ed work to anyone - i.e. Red Hat can prevent the GPL from applying between them and anyone by avoiding any action that would trigger the GPL.
2. Once Red Hat distributes a GPL'ed work to someone, that someone can come back at any time in the future asking for the corresponding sources.
3. Red Hat does not prevent customers from redistributing the RHEL source code (they can't).
4. Having distributed some version of a GPL'ed work to someone does not force Red Hat to distribute a different version to that someone. See 1.
A simple search on "Linux GPL-2 license" yields "The Linux Kernel is provided under the terms of the GNU General Public License version 2 only", and on the gnu site, "Accompany it with the complete corresponding machine-readable source code [...or...] give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code". For brevity, I synopsized this in my comment.
I see too many articles saying that Red Hat only have to provide source code to its customers - and the blog only implies that - but the Linux license requires more. The community often takes the source code, compiles and matches the binaries. That is essential. Red Hat offers a service, support and warranty, but as the license says, you cannot just take the source code, you have to give it back too.
I had a contract where source code had been lost, until I found a printout, yellowed and wrinkled, showing self-modifying code to boot, and assembled that, finding a match to the binary, at which point I could produce a module that could be maintained in the future. That task would have been much more difficult without source code.