Disclaimer: I am not a lawyer.

So DPL-licensed patents can never be used offensively in the future, but wouldn't they also greatly reduce the inventor's chances of ever making any money with their patent?

Large corporations will just use your patent for free, because their own patents are held by separate shell companies, so they are "part of the DPL network" by default.

And if you can't make any money with your patent, why make a patent? It's costly and complicated. Might as well just publicly disclose the invention (in a legally acceptable way), and the result will be the same as filing a patent under DPL.