And good luck finding a hardware manufacturer willing to produce devices with your forked version thanks to Google's draconian agreements with manufacturers.
“the agreement places a company-wide ban on Android forks, saying OEMs are forbidden from taking ‘any actions that may cause or result in the fragmentation of Android’ and specifically disallows distributing or encouraging a third-party to distribute ‘a software development kit derived from Android.'”
Not so very open after all?
The people who have forked android have great difficulty finding OEMs to manufacture thrir devices as the list of those who don't have agreements with Google is rather short.