There is a huge graveyard of projects that companies "donated" to the community. Think of Solaris operating system, Google Wave. Typically, I am not saying that this is IBM case, but typically it means that a given product does not bring much value for the company and usually this means that a given product does not have too much value at all.
Enterprises are rarely giving something away, they should earn money, so if they do this, it rises suspicion that there is a product that has no value and a company gives away something worthless only for the sake of PR.
There are exceptions, though. Blender failed to make money for the studio that made it, resulting in them selling it to the community for a one-time fee, and it is now one of the great jewels of the open source movement: https://www.blender.org/foundation/history/
It's important to note, though, that in Blender's case the founder remained involved the whole way through, and I think still is. I suspect his dedication and long-term attention is a lot of why it worked out.
OpenSolaris is still alive via forks and parts of it are routinely distributed with Linux and BSDs. Solaris is still proprietary, of course, and is as niche as AIX.
What is concerning here is that opening SPARC did not create a vibrant ecosystem of SPARC parts and computers, which is a shame.
As I see, IBM has the high end well covered with POWER9 and 10 and I'm not sure the embedded PowerPC crowd is that interested in big brother's ISA.
The key difference can be that while SPARC was stagnant when it was opened, POWER is extremely successful (and took over much of what was previously owned by SPARC and HP)
Compared to what? To the meteoric rise of x86 in the data center, and ARM in embedded, not enough it seems?
And yes, currently the two largest supercomputers (Sierra & Summit) are POWER machines, but 1) Most of the oomph in those come from the Nvidia GPU's not the POWER cpu's 2) IBM got none of the CORAL-2 systems, which makes people wonder whether they have given up on the HPC market.
If anything, it seems POWER is on a slow descent towards irrelevance. Considering the nice moves they have made wrt. openness (e.g. the Raptor machines with open firmware all the way down to the metal etc.), I hope I'm wrong and this move helps turn the ship around. We'll see I guess.
POWER belongs to a niche. It's in the very profitable scale-up segment, above the x86 space, where x86s don't reach without some custom chipsets. The high end "reasonable" x86 boxes compete with the low end POWER machines and, from then on, almost nothing competes with them (it's a narrowing niche, I must add, and Oracle doesn't seem very interested in it). If IBM wants POWER to expand, it must do so down towards Intel and AMD.
IIRC, the time Sierra and Summit got designed, POWER offered interconnects faster than anything available on x86, which was important to keep the GPUs in those systems busy. Different HPC systems have different needs and with the latest Xeon Scalable and AMD Rome that advantage may have evaporated a bit - and I'm not surprised IBM didn't win or even propose. Let's see what OpenCAPI and OMI bring to the table and if, with the good experiences with the Talos desktops as proof that the software ecosystem is there some foundry gets interested in something that could compete with lower end Xeon in the embedded space.
Enterprises are rarely giving something away, they should earn money, so if they do this, it rises suspicion that there is a product that has no value and a company gives away something worthless only for the sake of PR.