[License-discuss] Shortest copyleft licence

[Tim Makarios]

On Mon, 2015-03-30 at 10:24 -0400, cowan at ccil.org wrote:
> That's pretty much what the Sleepycat license does.  Here's a very lightly
> edited version of its additional clause:
> 
>     Redistributions in any form must be accompanied by information
>     on how to obtain complete source code for the licensed software
>     and any accompanying software that uses the licensed software.
>     The source code must either be included in the distribution
>     or be available for no more than the cost of distribution
>     plus a nominal fee, and must be freely redistributable under
>     reasonable conditions. For an executable file, complete source
>     code means the source code for all modules it contains.
>     It does not include source code for modules or files that
>     typically accompany the major components of the operating
>     system on which the executable file runs.

I might have misunderstood it, but this seems like very weak copyleft to
me.  The (presumably possibly modified) source code could be made
"freely redistributable under reasonable conditions" that were
themselves a permissive licence, allowing the next person to
re-monopolize their own derivatives of the derivative work.  Or have I
missed something?

How about this for a licence?

The creators of this work affirm that anyone who obtains a copy of this
work is licensed to:
  * make further copies and derivative works from their copy of the
    work, and
  * use and distribute their copies and derivative works,
provided that all such derivative works are governed by this licence.

50 words.  It doesn't require making the source code available, but
recipients of binaries will always be free to make derivative works by
reverse engineering the binaries.  It does make itself incompatible with
other copyleft licences, though, which seems difficult to avoid in a
very short, non-weak copyleft licence.  I'd be keen to be proven wrong
on that point, though.

Tim
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