About The Code Playground
I have spent many years in the various Google Developer Groups helping out other developers with coding questions and using the (at the time) many Google API's (most prominently known for the AJAX and Gadgets APIs), which led to Google labeling me as an Official API Guru.
One day in the Google AJAX APIs Developer IRC channel I was talking with one of their developers at the time (Ben Lisbakken) who asked me what I thought Google could do to further help out its developer community. I said, well one thing I know that would greatly help us out would be a way to get around trying to post code in the developer groups which was notoriously bad for breaking code, plus it was hard to debug issues from the developer community.
I mentioned that we really needed a coding sandbox where we could load and edit the code samples from the Google APIs and save the example code (How To...) and paste a link in the developer channels for the people in the groups (or anyone) to be able to use it as a starting point as well as have a way to explore it further. Ben thought this was a great idea and off he went to develop the Google AJAX APIs Playground.
After this, many other groups within Google (like Google Maps etc...) quickly embraced this project and used it to add their own samples into it which led to the Google API Playground we know today. :)
Open Sourcing Of The Project
I was very happy when Google decided to Open Source this project so others, like html5rocks code playground, could explore what went into creating the API Playground and be able to download and run their own instances of it as well.