The Interactive Intelligence Developer Portal has open source projects available for reference or for the development community to fork, extend, and enhance. The organization can be found at https://github.com/InteractiveIntelligence/.
Here you will be able to find simple example projects as well as complete applications. These projects are hosted under the Mozilla Public License 2.0 license which means that all code can be used in other open source or closed source projects as well as free and paid applications.
Community contributions to open source projects is strongly encouraged. First step is to get a free account on GitHub and become familiar with some of the basics of git. Next create a fork of the project you want to work on. GitHub has a good tutorial on how to fork a repo. Make any necessary changes in your repo and when you are ready to have those changes integrated back into the main repository, issue a pull request. GitHub again has a good tutorial on how to create a pull request.