I'm big on OpenStreetMap, but I can't deny its a bit of a liability for Facebook and other companies that display maps to their users. There is the occasional vandalism edit that simply can't be shown to an end-user. Facebook put significant effort into maintaining a moderated version of the OSM database that lags behind the real-time edits. Facebook, Microsoft, TomTom, etc. know this is a ton of work and want to pool their resources. Making it open also helps to openly compete with Google, the other big map data provider.
If you want to contribute to Overture as an end-user, AFAICT your best option is to edit OpenStreetMap and see if your changes eventually get pulled in. Overture has promised the OSM community that they'll make much of their data available to be contributed back, we'll see if that pans out.
When it comes to AllThePlaces -- as an OSM nerd it seems like there is an opportunity to build a better bridge between this and OpenStreetMap, to make it easier to quickly update businesses in an area. Recently there has been a pretty successful push to link OSM data with WikiData, using tools like the OSM ↔ Wikidata matcher [0]. For POIs, it's a lot of work to add a bunch of local businesses, even with tools like EveryDoor [1]. It would be so cool to see AllThePlaces integration into RapID for example, if there isn't already(?)