Unbelievable. Yet again, we have a post on finding x86 alternative that's most FOSS friendly. Yet again, the author is unaware of or ignores the only architecture that's open, has GPL cores, and an ecosystem. That's SPARC. Oracle's T1 and T2 cores are open-source to study. More appropriately, Cobham-Gaisler's Leon3 HW is dual-licensed under GPL and commercial. The Leon4 is 4-cores. SPARC ISA is open. Open Firmware ex…
But the SPARCs you mention have their drawbacks. LEON is not that competetive in the high end (in order single issue, low clock freq) and T1/T2 are only cores (i.e. without interesting "uncore" stuff) and not that good as general purpose "desktop like" CPU.
I have much higher hopes for RISC-V, the community is really booming and the architecture is better than SPARC.
I say this as a former Gaisler employee and SPARC proponent :-)