Embodied interaction has the potential to provide users with uniquely engaging and meaningful experiences. m+m: Movement + Meaning middleware is an open source software framework that enables users to construct real-time, interactive systems that are based on movement data. The acquisition, processing, and rendering of movement data can be local or distributed, real-time or off-line. Key features of the m+m middleware are a small footprint in terms of computational resources, portability between different platforms, and high performance in terms of reduced latency and increased bandwidth. Examples of systems that can be built with m+m as the internal communication middleware include those for the semantic interpretation of human movement data, machine-learning models for movement recognition, and the mapping of movement data as a controller for online navigation, collaboration, and distributed performance.