As we've seen with GPL'd code, many companies are happy to skirt the license restrictions if they feel that they can get away with it. How much money and effort would then need to be expended to enforcement of said new license for OpenBSD? How many companies would do a cost/benefit analysis of the likelihood of OpenBSD lawyers suing them, and even then ignore the license if they thought that it would be less expensive to risk a lawsuit?

"Change the license" isn't a silver bullet. Companies aren't machines that are fed licenses that they then obey like punch cards into an old IBM machine.