TL;DR AWS will either acquire MD next/soon, or (more likely) keep them around for the optics that they are totally not going to starve the community of anything other than DuckDB as a hosted AWS service.

From the MD "about page":

The idea for MotherDuck came after Jordan Tigani, MotherDuck co-founder and chief duck-herder, saw DuckDB in action and thought, “Wow, this is amazing! someone should really build a serverless version.”

...

Hannes and Mark, who founded DuckLabs to focus on the core technology and build the world’s best analytics database, were looking for partners who would build a commercial cloud offering.