According to OSM, they're complementary and they kind of work together:
Free and Open Source Software
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.
Pretty well thought-out statement. Looks like there are adults at the helm of OSMF. There might be money coming in like they do for Linux.
Given how much money Google Maps makes with its rate limitations, I can see why other companies want to launch their thing, unfortunately. OSM will remain the ethical option.
So it is a joint just to try to compete against Google maps? Makes a lot of sense now you mention it. I'm not planning to switch from OSM though!!
I bet there's something in OpenStreetMaps Licence that the "Steering Members" of Overture don't like.
I personally don't think it would replace osm, for what I just viewed on: https://bdon.github.io/overture-tiles/places.html overture poi are not really placed in the right spots and in my city there are some that are really ancient, so maybe that's why they don't want to contribute to osm directly, because they are not that good of a data, but they can become handy for a mapper that know the zone pretty well.