Comment by afiori
9 hours ago
My superficial understanding is that arm does not prevent from sharing implementation details of your own design but most chips also license a starting implementation that has such limitations. So the end result is often more restricted than the ISA licence some would require
Most ARM licensees aren't permitted to create custom implementations, only to use IP cores provided by ARM. There are a couple of companies who do have an architectural license, allowing them to create their own implementations, but there are only a few of those and they aren't likely to share. (It's also possible that the terms of their license prohibit them from making their designs public.)