In a bold move, Unity released almost all the source code for the new Unity UI system as an open source project via Bitbucket.org. This isn't the first time they have made things public; back in October 2014, Unity released their Unit Test Tools and a bunch of examples on their new public account (check them all out at https://Bitbucket.org/Unity-Technologies).
Note
Note: This section assumes you have either Visual Studio (2012+ express/community, pro, or ultimate), MonoDevelop, or Xamarin Studio installed to build and edit code. By default, you should already have MonoDevelop installed when you installed Unity.
You can browse the code all you like on the website, but to build/use it on your machine you will need a code editor and code build engine.
This is however, the first time they have released a core part of the Unity Engine for all to see (there have been a few other side projects but this is the biggest so far), to break it apart and even replace it in your...