Yes. There were a number of rapidly developed versions up to X10 in 1986, which was the first one released under a free license (and thus the first one widely a

Yes. There were a number of rapidly developed versions up to X10 in 1986, which was the first one released under a free license (and thus the first one widely adopted). X11 was an overhaul of X10 intended to increase portability/compatibility, and also the first version developed as a community open source project rather than internally to MIT. That came out in 1987. As for why X11 was the last major version: the protocol has remained backwards compatible since then. Clients created decades ago can still operate with modern X servers. It's pretty cool! http://www.theresistornetwork.com/2013/12/a-testament-to-x11-backwards.html http://www.theresistornetwork.com/2013/12/a-testament-to-x11...