> company B is liable for A's costs to develop the new system No, just for the difference between the cost of developing system A' that could have been develop

> company B is liable for A's costs to develop the new system No, just for the difference between the cost of developing system A' that could have been developed instead of A had it not been for the requirement for going around patent of company B that has since been invalidated. But good luck estimating that. Also since you're liable to pay for the consequences of future invalidation of you patent, the damages should be capped to the profit you've earned so far from the pattern to make things sensible. > It would be like demanding that your competitor subsidize your R&D This seems pretty fair if you've been on the market for much longer and did a lot of R&D. It would also move the balance a bit from competition to cooperation even if it would be labeled as anti-capitalist by some. It would also incentivize you to open-source and patent something, instead of keeping it closed but not patenting (both keeping all implementations of a patented algorithm closed and patenting it should not be allowed, at least one open-sourced fully working proof of concept should be required). You could still get a profit from the patents that came out of your R&D, even if your company failed, but a younger competitor that benefited from your exploration succeeds, which would probably incentivize more R&D spending! To go even further you could force attribution of pattents to individuals and never companies (even if they could end up owned in majority by your investors and not yourself), so that a company's bankruptcy and debt don't also suck the "profit from invention" into its black hole. ...but of course, I can't dream of such sensible systems of law until we have an above-human-level-AI actually writing the laws for humans to follow, hopefully for our own good :)