This paper presents the implementation of an open-source 6-DoF pose estimation system for micro-air vehicles and considers the future implications and benefits of open-source robotics. The system is designed to provide high frequency pose estimates in unknown, GPS-denied indoor environments. It requires a minimal set of sensors including a planar laser range-finder and an IMU sensor. The code is optimized to run entirely onboard, so no wireless link and ground station are explicitly needed. A major focus in our work is modularity, allowing each component to be benchmarked individually, or swapped out for a different implementation, without change to the rest of the system. We demonstrate how the pose estimation can be used for 2D SLAM or 3D mapping experiments. All the software and hardware which we have developed, as well as extensive documentation and test data, is available online.