The Material Design guidelines are a sort of path for developers to follow when looking to update the UI of their apps, as Google wants users to be able to experience the stunning visuals for all apps that they do with Google's creations. Google first introduced Material Design when they announced the developer preview of Android 5.0 Lollipop known simply as Android L, which they showed off during Google I/O back in 2014. People's first taste of this was through the official Google I/O application which Google routinely sends out ahead of the conference annually so event attendees can plan their trip accordingly for sessions to visit and get the layout of the conference. Google also used the app as a reference for developers to show how to implement material design.
This year Google has done the same thing with the 2015 version of the Google I/O app with one major difference. This year's app is full Material Design with the deep colored header bar, transparent status bar, transitions, etc. Google has posted the app's code up to Github so that developers are able to poke around in it and give things a look, which should aid them in applying the same sets of material design standards to their own applications. Not only can the source code for the app teach developers some things they may not already known in regards to Material Design, but it can also inspire developers to introduce something visually which they may not have thought of before.
If you're a developer looking to bring some flair to your application, this source code is likely something you'll want to mess around with, even if just for a little bit. If you're not a developer but you still understand the process and the nature of coding, you can still play around with it to check things out. The code should now be readily available for anyone who wishes to mess with it, and sometime in the coming months ahead Google states that users should look out for more updates to it. What those updates will bring is unclear, but it's likely that whatever it is it will be for the purpose of giving developers more to work with.