So, how can a group of volunteers scattered all over the world actually create, maintain, and develop an operating system? Almost all discussion takes place via email and online chat. This can be slower than a face-to-face meeting, but is the only means by which people everywhere in the world can openly and reasonably communicate. This also has the advantage of providing a written record of discussions.
OpenBSD has three tiers of developers: the contributors, the committers, and the coordinator.