Re: Dual-licensed wikibooks

This issue comes up so often, I've had plenty of time to revise and
perfect my response to it. Dual Licensing is permitted, in theory, but
in a much more limited way then what some of our authors intend. The
most that an author can do is assert that a particular revision of a
particular page is dual licensed, and only if all previous authors (if
any) maintain that assertion. If any author edits a page that was dual
licensed and chooses to go GFDL-only on their contribution, the page
is no longer dual-licensable (but previous revisions still can be, if
viewed from the page history).

Imagine a book donation where the donated book is GFDL+X (where X is
some other free license). The very first uploaded version of that book
also can be marked as being GFDL+X, and a link can be made to the
original source with an indication that the original will always be
GFDL+X even if future revisions at Wikibooks are GFDL-only.

Many books with complicated arrangements like this may wish to devote
an entire page for the purpose, such as "/Licensing" or whatever. A
simple notice such as "The original revision of this book as uploaded
on mm/dd/yyyy is released under license GFDL+X and is available from
LINK".

Besides this arrangement, there isn't anyway for a book to be dual
licensed and to remain dual licensed while it's on Wikibooks. We could
try to implement some kind of complicated opt-out ("remove this
template if you choose to make your contributions GFDL-Only"), but
that's not really feasible in the long-run and will only lead to
confusion ("But I didn't see the notice!").

In general, besides original versions where the author wants to make
clear that an alternate source for the book is released under a
dual-license scheme, we can't really support dual-licenses.

--Andrew Whitworth