Copyright \= \copyright{} 2003--2005, 2008, 2014--2015, 2018 \hspace{1.mm} \=  \kill

Copyright \> \copyright{} 2018 \>  Chestek Legal. \\

\section{GPLv2 Irrevocability}

There are two legal theories why a contributor cannot terminate their license

grant. First is an argument that the text of the GPL prevents it; second is

that a contributor would be estopped from succeeding on an infringement claim

for continued use of the code even if it wasn't removed.

\subsection{The text of the GPLv2}

The GPLv2 have several provisions that, when taken together, can be construed

as an irrevocable license from each contributor. First, the GPLv2 says ``by

\emph{modifying} or distributing the Program (or any work based on the Program), you

indicate your acceptance of this License to do so, and all its terms and

conditions for copying, distributing or modifying the Program or works based

on it'' (GPLv2\S5, emphasis added).  A contributor by definition is modifying

the code and therefore has agreed to all the terms in the GPLv2, which

includes the web of mechanisms in the GPLv2 that ensure the code can be used

by all.

More specifically, the downstream license grant says ``the recipient

automatically receives a license from the original licensor to copy,

distribute or modify the Program subject to these terms and conditions.''

(GPLv2\S6). So in this step, the contributor has granted a license to the

downstream, on the condition that the downstream complies with the license

terms.

That license granted to downstream is irrevocable, again provided that the

downstream user complies with the license terms: ``[P]arties who have

received copies, or rights, from you under this License will not have their

licenses terminated so long as such parties remain in full compliance''

(GPLv2\S4).

Thus, anyone downstream of the contributor (which is anyone using the

contributor's code), has an irrevocable license from the contributor. A

contributor may claim to revoke their grant, and subsequently sue for

copyright infringement, but a court would likely find the revocation was

ineffective and the downstream user had a valid license defense to a claim of

infringement.

Nevertheless, for purposes of argument, we will assume that for some

reason the GPLv2 is not enforceable against the contributor\footnote{For

  example, the argument has been made that there may be a failure of

  consideration on the part of the contributor. While \textit{Jacobsen

    v. Katzer}, 535 F.3d 1373 (Fed. Cir. 2008) is accepted as holding that

  there is consideration received by the contributor in a FOSS license, the

  posture of the case was one where the contributor advocated for the theory,

  not against it. The author is not aware of any other decisions that have analyzed

  the question in any depth, so it perhaps could be challenged in the right

  factual situation.}, or that the irrevocable license can be

revoked\footnote{A contract without a definable duration can be terminated on

  reasonable notice. \textit{Great W. Distillery Prod. v. John A. Wathen Distillery

  Co.}, 10 Cal. 2d 442, 447, 74 P.2d 745, 747 (1937). The term nevertheless

  can be a term of indefinite length where its continuing effect is tied to

  the conduct of the parties. \emph{Id}.}. In that case, the application of

promissory estoppel will likely mean that the contributor still cannot

enforce their copyright against downstream users.

\subsection{Promissory estoppel}

``Promissory estoppel'' is a legal theory that says, under some

circumstances, a promise is enforceable against the promisee even after the

promisee tries to renege on the promise. The test for how and when promissory

estoppel applies differs from state to state, but generally where there is a

``promise which the promisor should reasonably expect to induce action or

forbearance on the part of the promisee or a third person and which does

induce such action or forbearance is binding if injustice can be avoided only

by enforcement of the promise.''\footnote{\textit{Kajima/Ray Wilson v. Los Angeles

Cty. Metro. Transp. Auth.}, 23 Cal. 4th 305, 310, 1 P.3d 63, 66 (2000), \emph{citing}

Restatement (Second) of Contracts \S 90(1) (1979).} Breaking it down, it is:

\begin{enumerate}

\item where there is a clear and definite promise;

\item where the promisor has a reasonable expectation that the offer will

  induce action or forbearance on the part of the promisee;

\item which does induce actual and reasonable action or forbearance by the promisee; and

\item which causes a detriment which can only be avoided by the enforcement

  of the promise.

\end{enumerate}

In this case, the promisor is the contributor. This should be an easy

standard to meet in any widely used software.

\begin{enumerate}

\item The promise is contained in the GPL, which is a promise that one can

  continue to use the licensed software as long as the terms of the license

  are met.

\item A contributor knows that there is a broad user base and users consume

  the software relying on the grant in the GPL as assuring their continued

  ability to use the software (one might even say it is the \textit{sine qua

    non} of the intent of the GPL).

\item Users do, in fact, rely on the promises in the GPL, as they ingest the software

  and base their businesses on their continued ability to use the software.

\item Whether the user will suffer detriment is case-specific, but using

  Linux, a software program that is often fundamental to the operation of a

  business, as an example, the loss of its use would have a significantly

  detrimental, perhaps even fatal, effect on the continued operation of the

  business.

\end{enumerate}

\subsection{Conclusion}

Whether as a matter of a straightforward contractual obligation, or as a

matter of promissory estoppel, a contributor's attempt to revoke a copyright

license grant and then enforce their copyright against a user is highly

unlikely to succeed.