If I spend a year of my life and savings to write a new database, how do I make money? Can I make money and open source my work? How?
There isn't an easy answer. Open Source isn't always the right answer, and a whole lot of naive software developers are learning this the hard way.
Even in closed source, some of these business models are dumb with or without open source being in the mix. Think about companies like Citrix or VMWare who are essentially selling their customer book to Microsoft and to a lesser extent Amazon for virtual desktops, and to Microsoft, Amazon and Google in the server space. ISVs used to compete with each other to sell their stuff to run customer desktops or datacenters. There was no aggregation of their runtimes Now for most of the market they are competing with each other to rent their software on big platforms, which may opt to strangle them at any time.
On the open source side, people who need FIPS still buy RHEL. Frugal people who need FIPS buy Oracle. RHEL is still open source, and the cheapskates who rely on CentOS can still do so, they just don't get to ride on RHEL's engineering work backporting new fixes to old software. Elastic never had a sticky business model.
Elastic is just another app/database platform. Open source is a side issue with Amazon... the real problem is that ultimately, their ability to exist as a platform is ultimately in the hands of a few companies.