Grab is just one of the corporate contributors of OpenStreetMap, Grab's "own map" is not theirs, it's ours, "OpenStreetMap contributors" is the copyright holder, and copyright managed by the OpenStreetMap Foundation.

Grab is a Gold corporate member of the foundation, it means it pays EUR 15000 annually. You can see other corporate members here.

The license of the data is called ODbL, they call it open source in the article, but software licenses don't work well outside the software world, it's a database license. ODbL has one requirement: If you display the map, or any extracted data, you have to display the attribution text, which reads "© OpenStreetMap". In the article there is a map, and they don't display this attribution, so this article does not comply with the license of the map it tries to advertise...

This whole article sounds like an ad for Grab. More technological info about how Grab employees contribute to the map on the OSM wiki: https://wiki.openstreetmap.org/wiki/Grab

Edit: One more thing about Grab: they bought the Google Streetview alternative Kartaview in 2019 from Telenav. Kartview had a FOSS Android client, its old version is still on Fdroid. After the takeover Grab still published source changes and releases to Github, but Fdroid compatibility was broken at one point. In 2022 they changed the license of Kartaview, it's not open source anymore...

So it's the classic corporate take on open projects... if they could they would close down OSM and their data, but it seems like at the moment they get far more for that 15000 EUR. The wording of the article hints this, they call it "their" map...