XYZ Organisation has data for free download under licence N. Can I use it in OSM?
Approach the data owners, explain OSM, and seek written permission to licence their data under our licence or (for the avoidance of doubt) without any restrictions on use at all. Unless it is clear that the data can be used without restriction, please do not rely on your own legal interpretation of the licence. OSM is all about creating a freely and easily redistributable data set. Anything which taints the dataset or exposes OSM to possible legal action interferes with that objective. Even if you only want to use a minor part, or compare the sources, you should still seek approval in writing. The legal principles involved are not well developed, and the OSM community wants to develop a free and untainted dataset and not test any of the legal issues involved here. In short: be ultra-cautious.
