Sun GPLed the HDL code for the CPUs, not the synthesis results, nor the masks, nor the process hacks. A bunch of Verilog does not a product make. If all it took to compete in that space was a text editor then Intel wouldn't be kicking everyone's butts to the extent that they are.
And, frankly, the Niagra CPUs aren't such great shakes. 8 small/slow (i.e. shallow pipeline, ~1GHz) cores with wide (4-way) threaded dispatch vs. 4 big/fast (deep pipeline, 3GHz) core with 2-way hyperthreading. Meh. The Intel offering is just as good even in the most parallel workloads, and *much* faster for typical software. Both AMD and IBM have more compelling CPUs, IMHO.