It sounds pretty reasonable to be honest, youre allowed to share the code and theres no legal reprocussions for doing so but the company should be able to just stop sending you stuff if you do?
The GPL states that the company isn't allowed to distribute their modifications with those legal repercussions in the first place:
You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice [..] and give any other recipients of the Program a copy of this License along with the Program.
This is section 1 of the GPLv2 [1]. This plainly states that if The Company is distributing their code under GPLv2, their customers are plainly permitted to "copy and distribute verbatim copies of the Program's source code".
Their whole business model is based on a tortuous reading of this part of section 2:
If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.
Their claim is that they are shipping their patch set as a separate work from the Linux kernel, so that they're not bound by the requirement that "the distribution of the whole must be on the terms of this License", and they're free to choose whatever license they want for their patch set. However, since their patch set is in no way a separate work on its own, only a lawyer could make that case without blinking.
