MIPS wasn't opened up until they were already dead, and then almost immediately threw in the towel and joined up with RISC-V.

PowerPC basically the same, not opened until after it was irrelevant. OpenPOWER is in the same enterprise market as SPARC and IBM is not far from Oracle on the "do not engage litigious bureaucracy" chart.

MIPS didn't really open. They made a big deal about it, but it turned out to mean something to the effect of 'we'll open more of our build system to partners who pay for a traditional MIPS license. No third party MIPS cores. No general release of MIPS RTL.'