Their home page at ghost.org literally says "Ghost is a fully open source, adaptable platform for building and running a modern online publication" at the top.
However, I'm pretty sure a person that was really interested in self hosting would not have trouble figuring it out.
I don't necessarily think it's bad that they don't emphasize how to use the open source version. After all, it is a business.
"Being a non-profit means that the company has no shares. I don't own it. Hannah doesn't own it. Nobody owns it - it's an independent entity. The company makes money and pays expenses, salaries and taxes as normal - but there's no way for it to be bought or sold either in part (investment) or as a whole (aquisition). Any profit the company makes can only ever be reinvested, not distributed. We can't cash out. Ever. Also the entire product is open source and has no copyright. Anyone can do whatever they want with our code, for free."
For reference the mobile homepage only says "The professional publishing platform"