How do they do that? I thought OSM was licensed in such a way that if you combine it with other data, the whole thing needed to be released with the same license?
I am not a lawyer, but I would assume someone at Overture has deemed their license (the CDLAv2 [1]) to be "compatible" with ODbL. (edit: From the link in OP, the OSM-based data is being released with ODbL. I think I'm wrong about license compatibility. Again, not a lawyer.).
[0]: https://opendatacommons.org/licenses/odbl/1-0/ [1]: https://cdla.dev/permissive-2-0/
From a brief skim of the landing page, it looks like the OSM-derived content is not being offered permissively. See https://overturemaps.org/download/.
Are they releasing OSM data or OSM derived data on CDLAv2 anywhere, right now?
There was issue like this in past but it was resolved.