On contrary there are other companies that pretend to sell "open" product that are open like a bunker (to name a few try looking for business software from ERP to CRM to DMS etc) and those are not contributed to FOSS. Even if they both pay someone to develop FOSS code and publish it.
I hope to have being able to clarify that point in my limited English...
On complex codebase: FreeBSD codebase is not exactly simple and little, but it live on it own foot since decades, for instance? Emacs, Debian, ... the same. I do not intent that a project must run on casual contribution but simply that contributors must be subjects that need/desire such code so they contribute to it for their own sake like the Intel example above.