Can you alter the MIT license?

[Jules Bean]

On Mon, 15 Nov 1999, Scott Johnston wrote:

> 
> ----------
> >From: Jules Bean <jmlb2 at hermes.cam.ac.uk>
> 
> >In particular, the GPL says that you must make available the source of the
> >whole work.  Now this is an additional restriction on top the the MIT one,
> >but it's not in conflict with the MIT one - it doesn't ask you to do
> >anything you aren't allowed to do.
> 
> I see.  This is what Bruce must have meant (about adding terms to the MIT
> license that are not in conflict with the original terms).  Know of anyone
> doing this, adding a copyleft term to a non-copyleft piece of free software?

Not off-hand, I'm afraid.  I'm sure there are many examples around...

>  I've considered it doing this with ivtools, and asked for feedback from
> users.  I got one strong and well reasoned response that opened my eyes to
> the partially immutable nature of the MIT license.  Since then I have thrown
> out all the years of assumptions about the BSD license and am trying to
> rebuild my understanding from the ground up. 

Hmm.  Well, could you summarise the response?

Some possibly issues:

Is ivtools entirely your copyright?  If not, you can't relicense it
anyhow. If it's partly your copyright, you could get permission from all
the other copyright holders to do so (in writing, ideally!).

However, if you make significant changes to ivtools, you can copyleft
those changes.  You will never be able to stop someone backtracking by
unpicking all your work, and using the old version under the MIT license
[or, equally, simply finding an old version].  However, assuming that you
are improving the product with your copylefted changes, people are
unlikely to do that.  As a result, ivtools would gradually become more
copylefted... if you think that's a good thing.  [I do, but that's not
really the point here].

Jules

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