The GPLv2 is not a contract, it is a revocable license.

[svasthree]

The GPLv2 is not a contract, it is a revocable license.

Here is a paper explaining what the GPL is and is not:
http://illinoisjltp.com/journal/wp-content/uploads/2013/10/kumar.pdf

(With full citations).
(PDF attached)

Page 12 starts the relevant discussion.
Page 16 begins the explanation of all the ways the GPL is not a 
contract.

Later there is a short gloss of state law promissory estopple doctrines.
Remember: in the case of the linux kernel it, unlike other projects, 
omitted the "or any later version" codicil, and is only under version 2 
of the GPL, which makes no promise of irrevocability by grantor.

(Note: The SFConservancy recently chose to publish a "correction" that 
conflates clauses, within version 2 of the GPL, [that clarify that if a 
licensee's license is revoked by operation of the license for a 
violation of the terms, that sub-licensees licenses are not-in-turn 
automatically revoked] - [with an inexistent irrevocability doctrine 
within the text of the GPLv2])
(Additionally: Clause 0 of GPLv2 specifically defines the "you" in said 
clauses as referring to the licensee (not the grantor); the 
SFConservancy's conflation is shown to be ever more disingenuous)

The Linux Kernel License grant:
Is Not: a contract. [No breach of contract damages vs grantor if 
rescinded]
Is: a bare license akin to a property license.
And: There is no "irrevocable by grantor" promise in v2. [No promissory 
estopple defense]
.: Can be rescinded at will.

Attachment: kumar-gpl-licenses.pdf
Description: Adobe PDF document