Re: Anti-TPM clauses

[Ben Finney <bignose+hates-spam@benfinney.id.au>]

Olive <olive001@tele2allin.be> writes:

> Ben Finney wrote:
> > Freek Dijkstra <debian2007@macfreek.nl> writes:
> >> Relevant part, in article 4a of
> >> http://creativecommons.org/licenses/by-sa/3.0/legalcode
> >>> You may not impose any effective technological measures on the
> >>> Work that restrict the ability of a recipient of the Work from
> >>> You to exercise the rights granted to that recipient under the
> >>> terms of the License.
[...]
> >> it's probably non-free, and best not put it in main. Correct?
> >
> > That's my understanding, yes. Largely on the basis that it's
> > imposing a non-free restriction ("You may not ...") on the
> > recipient.
> 
> Could you please tell more. The very purpose of copyleft is to forbid
> to prevent someone distributing a covered work by forbidding the
> recipient to exercise his "right".

Not quite. The purpose of copyleft is to use copyright license terms
to ensure that all recipients can exercise their freedoms. Where
necessary, restrictions are imposed to ensure this; but that's not the
only way (as can be plainly seen from the GPLv3's solution to this
same issue).

> Even in GPLv2 there is this term (par 6):
> 
> "You may not impose any further restrictions on the recipients'
> exercise of the rights granted herein"
> 
> It seems that the restriction in the creative common is just a subset
> of this.

The important difference is that the CC by-sa license terms impose a
restriction on *means* — "you may not do such-and-such to the work" —
even where that doesn't effectively restrict the recipient's freedom.

The use case I've seen discussed is that of providing the same work in
two forms to the same recipient: one that has "effective technological
measures" that restrict access (e.g. media that the recipient wants,
but that mandates DRM), and one that is free of such measures.

Even though every recipient would thereby have full exercise of their
freedoms in the work, the redistributor is forbidden to provide the
work this way, which is a non-free restriction.

By contrast, the GPLv3 allows the above, but explicitly disclaims the
result as being an "effective technological measure", to disarm the
possibility of suing the recipient for circumventing the measure if
they choose. It imposes no restriction, *and* explicitly disavows
another restriction that might otherwise apply.

-- 
 \           "Kissing a smoker is like licking an ashtray." —anonymous |
  `\                                                                   |
_o__)                                                                  |
Ben Finney