It depends on the dataset, ultimately, but our opinion is that if we are allowed to give the data away, we will. But we also want our open data to be seen as authoritative and high-quality. In our department, nearly all of our layers are derived from publicly-available documents, anyway, so we feel that derivative products should be public as well. Parcels, zoning, centerlines, etc. If you knew what you were doing, you could read the deeds and draw them up yourself, so why not save you the time and give you the "official" version? There are other datasets that we use that aren't as "official", such as building footprints, hydrology, etc., and we're working on moving those to OpenStreetMap entirely, and plan to direct interested users to the many ways of extracting data from the OSM dataset. The end goal is essentially to maintain free and open access to anything that we are the authoritative source for, and to offload the rest of it, and make it even easier to access as part of a global, open dataset.
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