Note that the study does not actually measure ROI from a revenue perspective, but estimates based on theoretical saved costs: The company invested $1M in open source infrastructure and potentially saved $2M in direct development costs (given that the code base is current worth $3M). [1]
Most interesting takeaway for me is the implications of open source for government funded projects, and a ratification of the idea that contributions of code for some public tool can save the general public tax money. A forward thinking org could try to broker some sort of tax cut based on SLOC contributed to public, government-sponsored projects? Maybe that already exists.
Would suggest studying Red Hat's rise to $2B in yearly revenue to understand how a company takes open source and turns it into revenue.
[1] GFDRR’s direct and in-kind investment in GeoNode over the past six and a half years has been in the range of $1.0–$1.5 million USD...GFDRR’s investment in GeoNode would be a reasonable amount even viewed strictly as a software development cost: the GeoNode software today represents an approximately 200% return on investment in terms of code written, since the current GeoNode project would most likely have cost $2.0–3.0 million USD if GFDRR had produced it alone as proprietary software, without building an open source community around the codebase.