>If company B sells a library for 0.01$ per unit and company A incorporates that in their next product that sells by the million they don't have to worry about people suing them for whatever B did. They have a contract, a library and some header files.
Of course they do, Company A infringes on the copyright regardless of the license deal they have with Company B. The only "thing" that they have is that they can sue Company B for the damages that Company A suffered due to Bs infringement.