Problems in Open Source Licensing

John Cowan cowan at
Mon Feb 17 05:26:45 UTC 2003

Jeremy Malcolm scripsit:

> [L]et's take
> the simpler case of releasing my own code under the GPL.  Do you see
> anything that would prevent me from withdrawing those licensing terms? 
> Short of contract or estoppel, and assuming that I adequately
> communicate the revocation of licence to my users, how can I be
> prevented from changing the licensing terms whenever and however I like?

I think there are three cases:

1) Users who have already relied on the GPL to distribute or modify your code

2) Users who are at present relying on the GPL to distribute etc.

3) Users who intend in the future to rely on the GPL to distribute etc.

As to case 1, I think you are pretty clearly estopped from doing anything
about their existing distributions or modifications; they relied on your
licensing terms in good faith.  Case 3 users, OTOH, are screwed.
Case 2 is obviously intermediate.


> Licence conditions have to be reasonable, contract conditions don't.  

Excellent.  That means the infamous MSOSL, which I bruited about onthis
list a few years ago, can be freely dismissed.  (This was a putative
Open Source license which required the licensee to consume moose
by-product as a condition of the license, for those of you who have
mercifully forgotten.)

John Cowan               cowan at
To say that Bilbo's breath was taken away is no description at all.  There
are no words left to express his staggerment, since Men changed the language
that they learned of elves in the days when all the world was wonderful.
        --_The Hobbit_
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