Ruth Hill Useem developed the term Third Culture Kids (TCKs) forty years ago to describe the children of military, diplomatic, missionary, and other families who exist in a twilight world between their passport countries and the countries in which they live. Often, these children are neither at home in their birth culture nor in the culture in which they live day-to-day, a fact that often becomes evident only upon returning to their native country. TCKs usually feel more at home with other TCKs than with other people.

In a somewhat similar way, FOSS communities often create their own culture, which is not the native culture of any of the participants. When Chinese developers work with Brazilian colleagues day after day, their communication does not usually reflect much of either Chinese nor Brazilian culture. When joined by colleagues from (say) Morocco, Russia, Canada, and Australia, native culture is made even less significant. Over time, the communities build up shared experiences, humor, social norms, and conventions that define that community, building up a synthetic third culture.

This is not unique -- collaborative groups have always developed their own sense of identity. The difference with most FOSS communities is that the collaboration is remote, so the participants remain in their native cultural context while participating in the synthetic third culture of the FOSS community, and the interaction is high-volume and sustained over a long period of time (decades, in some cases). Obviously, the diversity, intensity, and health of the community play a significant role in the depth and uniqueness of the third culture.