I'm aware that individual implementations of the ISA are nonfree. There's still a huge benefit to using the free ISA, because we can target nonfree hardware while necessary and our software will just work on free hardware when it's available. There are already some free low-power designs, and if RISC-V gains traction I expect some free high-power designs to come out of the woodwork.

A robust open processor ecosystem could be the impetus for a huge improvement in open-source EDA tooling and public EDA research. Even now, the absolute cutting edge in HDL research is free and open-source (and 100x more user-friendly than anything to come out of Xilinx or Altera), and I suspect the same would happen for silicon-targeting synthesis tools if there was a demand for it.

The idea would be to get 90% of Intel's performance for 5% of the work. Intel spends insane amounts of money on manual routing and optimization, extensive testing at every stage of prototyping and production, stuff like that. The creative laziness of the free software/hardware people could probably improve on that very substantially with minimal losses to the finished product.