Each part of the d:swarm data management platform is open source. Hence, everything is available for free at the World Wide Web. Please have a look at our d:swarm organisation at GitHub.
…yes, there are more then one repository. So please have a look at the structure overview and architecture for details.
If you wanna participate as a developer, then please follow the developer install instructions (that slightly differ from our server install instructions). We have some instructions for pushing code to our repos as well (but don’t take them too serious – each pull request is welcome 😉 ).