> "Advantage: they self-replicate royalty free, something the nanobot company would never allow."

Such restrictions, or similar, might be a good idea in general. A gray-goo excursion would not be fun. Algae blooms cause enough damage as it is, and at least there are things that eat algae.

Just evolve to eat metal. Easy. There. All is fixed.

You just need a DRM server which each nanobot must obtain a proper license key from every cycle.

Monsanto disagrees.