If installing these things required passing FDA trials before you could even do the first install, it’s hard to imagine anyone self funding the regulatory trial and then open sourcing the result.
These businesses you mention are different because you can start getting paid as soon as you build some expertise in how to operationalize the systems.
How many hospitals download the linux kernel and manage their own servers?
I would assume very few. They likely lack the expertise, and pay third party companies to manage the servers, patches, and updates for them... even when the software is open source.