What is Open Space? There are a number of useful sources for answering that question.
Probably the most authoratative text is the book published by Harrison Owen. He is credited with having created and popularized the use of Open Space, beginning in the 1980s. He wrote this book as a guide to convening OS and states on p. 153:
Open Space is now a global phenomenon. What began as the special preserve of a select few is now a broadly held property. At the moment, the vast majority of Open Space events are facilitated by people I don't know, have never seen, and that is just wonderful.
Owen, H. (1997). Open space technology: A user's guide, 2nd Ed. San Francisco: Berrett-Koehler Publishers, Inc.
Call number at SFU Harbour Centre library: HD 30.23 O927