Right to distribute modifications?

[Bjorn Reese]

John Cowan wrote:

> AFAIK the free software community has always understood the right
> to distribute modifications to be implied by this license, but
> of course (as usual) no court has spoken, and so nobody can say
> for sure.  RMS is being cautious, that's all.

Then what differentiates the right to distribute the software with
modifications from, say, the right to use the software with
modifications (which relates to the FSF's freedom 0), to warrant
explicit caution?
--
license-discuss archive is at http://crynwr.com/cgi-bin/ezmlm-cgi?3