Grsecurity is a patch for the Linux kernel which, it is claimed, improves its security. It is a derivative work of the Linux kernel which touches the kernel internals in many different places. It is inseparable from Linux and can not work without it. it would fail a fair-use test (obviously, ask offline if you don’t understand). Because of its strongly derivative nature of the kernel, it must be under the GPL version 2 license, or a license compatible with the GPL and with terms no more restrictive than the GPL. Earlier versions were distributed under GPL version 2.
Currently, Grsecurity is a commercial product and is distributed only to paying customers. My understanding from several reliable sources is that customers are verbally or otherwise warned that if they redistribute the Grsecurity patch, as would be their right under the GPL, that they will be assessed a penalty: they will no longer be allowed to be customers, and will not be granted access to any further versions of Grsecurity. GPL version 2 section 6 explicitly prohibits the addition of terms such as this redistribution prohibition.
By operating under their policy of terminating customer relations upon distribution of their GPL-licensed software, Open Source Security Inc., the owner of Grsecurity, creates an expectation that the customer’s business will be damaged by losing access to support and later versions of the product, if that customer exercises their re-distribution right under the GPL license. This is tantamount to the addition of a term to the GPL prohibiting distribution or creating a penalty for distribution. GPL section 6 specifically prohibits any addition of terms. Thus, the GPL license, which allows Grsecurity to create its derivative work of the Linux kernel, terminates, and the copyright of the Linux Kernel is infringed. The contract from the Linux kernel developers to both Grsecurity and the customer which is inherent in the GPL is breached.
(Score: 4, Insightful) by requerdanos on Thursday July 06 2017, @03:48PM
There's interesting reading on this topic at grsecurity's web site, where they explain [grsecurity.net] that certain features are present in the, quote, "grsecurity kernels":
(Emphasis added)
grsecurity makes a strong case on this page that their product is a derivative of the stock Linux kernel, to which their grsecurity kernels are directly compared.