[darcs-users] how to redistribute darcs+Eclipse (was: Darcs API?)

zooko at zooko.com zooko at zooko.com
Sun Apr 17 13:51:29 UTC 2005


There is another issue here aside from the common question of whether your
code ought to be GPL'ed or not.

You could take Eclipse and GPL'ed darcs and combine them into one combined
package and redistribute it, except for the "patent retaliation clause" which
makes EPL incompatible with GPL.

The Eclipse Public License is GPL-incompatible *only* because of it has a
clause disallowing people from using Eclipse while suing other people for
patent infringement of a patent that applies to Eclipse.  The GPL requires
that you allow other people to use the software freely (even if those people
are currently suing you for patent infringement).  Therefore, you cannot
redistribute a combined work comprising a GPL'ed component (use this combined
work freely, even if you are suing me for patent infringement of a patent that
applies to this software) with an Eclipse component (use freely, unless you
are suing me for etc.),

If the copyright holders of darcs wanted to allow people to distribute Eclipse
combined with darcs, they could amend the darcs license with a "special
exception" that says you are allowed to redistribute darcs combined with
EPL'ed software.  This would not, as far as I know, violate the intent of
David Roundy and the others that darcs be GPL'ed.  In particular, doing this
would *not* allow darcs to be used as a module in a proprietary combined work.

See for example the FSF's recommendation about making a special exception for
QPL'ed programs in [1].

Another workaround would be if the FSF ever got off its great big glacial butt
and published a new version of the GPL.  Since the license of darcs states
that people may use it under GPL v2.1 or at their discretion any later
version, people could then use darcs under this hypothetical new version of
the GPL.  The next version of the GPL will hopefully be compatible with the
EPL, which would then allow people to start redistributing Eclipse combined
with darcs with no further effort on the part of the authors of darcs.  The
reason I have this hope is that the FSF states on their "license list" page
[1] that they have no objection in principle to Eclipse's "patent retaliation"
clause.

So in short, darcs *could* be legally combined with Eclipse if either (a) the
copyright holders of darcs said so in a legally binding way or (b) the FSF
published a new version of GPL which was compatible with EPL.

In the meantime, you are still allowed to *use* Eclipse combined with darcs on
your own system, you are just not allowed to redistribute it to other people.

Regards,

Zooko

[1] http://www.fsf.org/licensing/licenses/license-list.html




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