Some open content Wiki sites use the [http://www.gnu.org/copyleft/fdl.html Gnu Free Documentation License] for their work. For Wikitravel, this license doesn't meet our [[Wikitravel:goals and non-goals|goals]], so we've chosen a different one instead.
The GFDL is specifically oriented towards software manuals and other textbook-sized references. For Wikitravel, we really want to have each article redistributable on its own. Specific requirements of the GFDL -- such as requiring that all copies of the work be distributed with a copy of the GFDL, a changelog, or that "transparent" (i.e. source) versions be available if you distribute over 100 copies -- make that harder.
It's easy to imagine some small "publishers" who might want to have simple photocopied printouts of Wikitravel articles:
*Local tourist offices
*Hotels or guesthouses
*Exchange student programs
*Wedding or event planners
For an article of 1-2 printed pages, it just doesn't make sense to require people to pass out another 10 pages of legalese text, as well as floppy disks or CDs full of [[Wikitravel:Wiki markup|Wiki markup]].
The license we've chosen, the Creative Commons Attribution-ShareAlike 1.0, is much easier and more lightweight. We think that using the Attribution-ShareAlike 1.0 license meets our goal of having [[Wikitravel:copyleft|copyleft]] protection on Wikitravel content, without putting an excessive burden on small publishers. All that needs to be included are copyright notices and the URL of the license; this can be done in a short paragraph at the end of the article.
The big downside of not using the GFDL is that GFDL content -- like Wikipedia articles -- '''cannot''' be included in Wikitravel articles. This is a restriction of the GFDL -- you're not allowed to change the license for the content, unless you're the original copyright holder. This is kind of a pain for contributors, but we figured it was better to make it easy for users and distributors to disseminate Wikitravel articles.