Three new proposed OSD terms

John Cowan jcowan at
Fri Mar 4 01:51:05 UTC 2005

Michael Poole scripsit:

> I would call these groups non-copyleft, weak copyleft and strong
> copyleft respectively.

I shall use the terms "permissive", "weak copyleft", and "strong
copyleft" in the hope of minimizing confusion, because unfortunately
the FSF uses "non-copyleft" to cover both permissive and weak copyleft

> Other OSI approved licenses are also strong
> copyleft in that they require larger works to use the same or a
> compatible license; the QPL is one example.

The QPL is an oddball in more ways than one.  It's not a strong copyleft
license exactly, because larger works need not be licensed under the QPL
itself: all that's required is that the binary and source forms of the
larger work be freely redistributable.  For example, you can combine
QPL and MPL components and license the result under the MPL.  The QPL
doesn't mix with the GPL, however.

> Proliferation of weak or non-copyleft licenses still requires that
> somebody do the work to determine license compatibility.  Since that
> analysis could be reused, I will concede that that work is not
> necessarily a "serious impediment."

First of all, someone must determine which licenses are permissive,
weak copyleft, and strong copyleft.

> Licenses worded like MPL v1.1 are particularly worrying for patent
> owners, since they purport to terminate the granted rights as of the
> first use, distribution, etc., by the user, rather than as of the
> filing of the complaint.  In a way, they work like an "extra strong"
> copyleft for patents.

Fair enough.

John Cowan  jcowan at
"In the sciences, we are now uniquely privileged to sit side by side
with the giants on whose shoulders we stand."
        --Gerald Holton

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