Foursquare is opening up Pilgrim, its proprietary location-based technology, to authorised developers for the first time.
In a Medium post, its president Stephen Rosenblatt explained:

"By opening up Pilgrim SDK to select innovative brands and companies with big ideas, we’ll add new and meaningful layers to our body of learning and continue to experiment."
Pilgrim delivers "the ability to precisely understand where phones go in the real world in real-time", modestly described as Foursquare's superpower. It is the core tech for all Foursquare's contextual tools.
Clearly, travel app developers are on its radar. The post references some travel use cases but there are no named travel firms among the private beta partners named.

"A traveler walks out of a hotel lobby, ready to explore a new city, so the hotel’s app pings them with suggestions of places they’ll love nearby (the closest yoga studio for the yogi, the local brewery for the beer-lover)."
Pilgrim SDK can also natively integrate with mobile marketing automation and analytics specialists such as Urban Airship, Appboy, Localytics, mParticle and others.
The availability of Pilgrim to travel app developers connects with the "live like a local" zeitgeist and taps into the desire of travellers (and locals) to find things to do and places to eat, in the moment, based on their actual location.
Having said that, Foursquare is active in travel on a B2B and B2C level. It recently signed a deal with Airbnb, licensing its images for the "live like a local" cheerleader in chief to use in its City Guides.
At the start of 2016 Foursquare raised $45 million and soon after launched Trip Tips, its consumer-facing social planning tool.
The launch of Pilgrim SDK also connects with the trend towards "open" systems - tech giants allowing approved third parties access to their own proprietary tech.
The post doesn't talk about licensing fees or revenue models. It will be interesting to see how travel app developers respond and whether the desired "futuristic thinking and magical consumer experiences" come from nifty startups (who might be priced out) or the established players (who might already have partnerships in place).
Related reading from Tnooz:
Foursquare enters trip planning melee with Trip Tips (Jan16)
Foursquare thinks it can add some data magic to the travel industry (July 2016)