Premium is something like discontinuing JS engine people rely on, move to Graal where certain performance features are not free for everyone. Hidden test suite is like the JCK I can't download to test my non-OpenJDK-based open source Java impl against (or Harmony or whatever). Regardless of details, the point is that it isn't more open like a MIT licensed Rust, Go, (recent) .Net, etc. There are obviously differing levels of openness by language and runtime regardless of specifics and differing levels by stewards of these languages/runtimes to make money on them.
We're not discontinuing Nashorn, simply not investing more in its maintenance any with the resources we have, which we can put to better use; if someone else wants to step up -- they're more than welcome to. Rust, Go and .Net Core (I think .Net isn't open source) are much, much smaller than OpenJDK. They require far smaller investment from the companies/organizations behind them.
