Ghost stories

[Stephen J. Turnbull]

Aaron Bentley writes:

 > I suspect that adding the "Affero" clause would have induced grave
 > backwards-compatibility concerns, since the first two versions did not
 > have it.

No more than *any* other change to a copyleft license.  All copyleft
licenses are mutually incompatible, that's all there is to it.[1]  The
only way out is dual-licensing.


Footnotes: 
[1]  Yes, GPLv2, GPLv3, and GDFL are pairwise incompatible in all
directions.  Don't let the fact that 2 < 3 fool you, it has no
relevance to compatibility.  All that matters is that 2 <> 3.