Does this mean it's only free for small companies, in which case how is that defined?

It's always good to see free content - have you considered using an established licence, e.g. Creative Commons Attribution ( http://creativecommons.org/licenses/by/4.0/ )? This has the advantage that the licences are written by legal experts, and there is also much greater awareness of what the terms mean, and less risk of incompatibility with other licences.