AFIK, AngularJS was the result of improving and open-sourcing the code of a failed startup, after taking it to Google, adding a tone of features to the codebase and using it in internal projects before open sourcing it.
In wikipedia http://en.wikipedia.org/wiki/AngularJS is says "AngularJS was originally developed in 2009 by Miško Hevery and Adam Abrons [10] at Brat Tech LLC[11] as the software behind an online JSON storage service, that would have been priced by the megabyte, for easy-to-make applications for the enterprise. This venture was located at the web domain "GetAngular.com",[11] and had a few subscribers, before the two decided to abandon the business idea and release Angular as an open-source library"
I think here they mention it in the adventures in Angular podcast that Misko took it from a previous company which was a startup between him and another developer that did not went through -> http://devchat.tv/adventures-in-angular/001-aia-the-birth-of...
It might also have been here or one of the the Javascript Jabber Angular episodes (their search functionality seems to be down for the moment)
> after taking it to Google, adding a tone of features to the codebase and using it in internal projects before open sourcing it.
Are pretty unique circumstances, that don't really show that it's an easy thing to do usefully/succesfully, for projects that aren't taken into Google, have a ton of features added by paid Google engineers, and then are used by internal projects at google to work out further kinks and cow paths.