The USA’s National Science Foundation (NSF) has announced new 5G R&D projects focused on open source platforms, while acknowledging that mobile broadband networks had proved the hardest platform to implement in open source. This throws light on the burgeoning discussion about how far future 5G and 6G networks can, or should, be based on open source technology, as opposed to just open systems? The NSF operates a research center in Salt Lake City, Utah, called Platforms for Advanced Wireless Research (PAWR), and its new experiments are based on a 5G testbed called POWDER (Platform for Open Wireless Data-driven Experimental Research), which was first announced in 2019. The POWDER team has implemented open source software on top of an outdoor 5G…