Maven is an open source build system which is available from the Apache Maven project. In principle, you could use any build system to build an OSGi bundle. But Maven is strongly recommended for the following reasons. Firstly, because Maven is used to build the Fuse ESB product itself, all of the Maven artifacts that you need to build your own bundle project are likely to be already available from the fusesource Maven repository or from the Maven central repository. Secondly, Apache Felix provides a Maven bundle plug-in, which automates the process of packaging code as an OSGi bundle. Thirdly, Fuse ESB provides a collection of Maven archetypes, which can generate starting point code for your project, enabling you to get started rapidly.