It's not that hard to make a living, if you write custom software instead of selling products. The niche I'm aware is development of modules for Odoo (a kind of SAP alternative); I've worked for such a small bootstrapped company for years, and 90% of what we wrote was A/LGPL licensed. Most clients don't care if you release useful generic parts of the code as OSS modules, nor if you use such modules from other developers.

I know companies following this model all over the world: Spain, Brazil, India, Argentina, Venezuela, etc.