Umbraco CMS is open source, so developers can browse, build and modify its source code.
Our source code is hosted on github.com. To get access to the latest source bits, go to our project page and browse the latest commits. Individual change-sets can also be browsed and downloaded.
One of the biggest benefits of using Umbraco is that we have the friendliest Open Source community on this planet. A community that's incredibly pro-active, extremely talented and helpful.
If you get an idea for something you would like to build in Umbraco, chances are that someone has already built it. And if you have a question, are looking for documentation or need friendly advice, go ahead and ask the Umbraco community on Our.