Wikitravel:Cooperating with World Wiki
While there is clearly some overlap, there seems to be an ongoing conversation regarding the nature/goal of World Wiki (is it about "travel" or about "places") , but there are clearly going to be overlaps as well as differences that may allow cooperation.
 Sharing content
World Wiki and Wikitravel use incompatible licensing schemes. World Wiki uses the GNU Free Documentation License ("GFDL"), while Wikitravel uses the Creative Commons Attribution-ShareAlike 1.0 ("by-sa") license (see Why Wikitravel isn't GFDL for more details). Because the GFDL and by-sa aren't compatible, it's not possible to copy content, in most cases, between articles on World Wiki and articles on Wikitravel.
There are some ways to do it, though. If you are the sole creator of content on World Wiki, you can move it to Wikitravel; simply note on the talk page that you're relicensing it under Wikitravel's Creative Commons license. Moving content worked on by other people requires getting their permission first; since both projects share the copyleft spirit, this shouldn't be difficult. The process is the same for moving material from Wikitravel to World Wiki.