But why all the effort needed when you can simply use the open-source Java version called OpenJDK? It's virtually identical to Oracle's JDK, only without commercial support, and it's licensed the same way those other alternatives you're suggesting.
Besides, dotnet core would not be a better replacement: it's got a large corporation behind too, so nothing prevents them to do the same in the future.
Er... Well, I'm with you for a different reason than updating... I'm thinking that Oracle is just shifting the licensing ground too much for my comfort.