i think the issue is less "sustain a company" and more the unspoken qualifier "extremely valuable".
sustaining a small company offering commercial licenses or hosting or support or consulting or whatever for an open source product is not going to be that much more difficult than sustaining any other kind of small company.
the issue that I see most often are OSS devs not approaching the problem like a company would and startup founders looking to build a unicorn while also keeping some kind of purity wrt open source.
not everything needs VC investment with valuations measured in the tens of millions but everything does need some level of formal business development (even if that business is of the non-profit variety).
sustaining a small company offering commercial licenses or hosting or support or consulting or whatever for an open source product is not going to be that much more difficult than sustaining any other kind of small company.
the issue that I see most often are OSS devs not approaching the problem like a company would and startup founders looking to build a unicorn while also keeping some kind of purity wrt open source.
not everything needs VC investment with valuations measured in the tens of millions but everything does need some level of formal business development (even if that business is of the non-profit variety).