Wikivoyage:Cooperating with OpenGuides
OpenGuides don't have a lot of information about the project on their site, but it seems that their mission is somewhat different from Wikivoyage's.
The guides seem to be more oriented towards comprehensive listings of all restaurants, bars, pubs, etc., in a city, and to be making guides for a single city at a time. Wikivoyage, on the other hand, is more selective with listings for a city, and also deals with a lot of other types of information (getting in, getting out, sleeping, etc.), types of destinations (countries, regions, national parks, etc.), and types of articles (itineraries, travel topics, etc.). In general, OpenGuides seem more oriented to residents of a city, where Wikivoyage is oriented towards travellers.
Sharing content 
While many of these sites use CC-by-SA compatible licenses, there won't be a single overarching license for all the OpenGuides sites - it'll be arranged on a per-site basis. So, check before copying material.
Linking to OpenGuides 
Links to OpenGuides appear in the left-hand nav column, like Wikipedia or Open Directory guides. To link to an OpenGuide, add [[OpenGuides:"name of city"]] to the page, where name of city is the first part of the guide's URL. For example, London had [[OpenGuides:london]], and Saint Paul had [[OpenGuides:saintpaul]].