I'm a language implementor. I'm always excited to see interesting new language implementations. I think Silver is a neat project, and I'd be happy to talk to you about ways you could efficiently implement full value semantics in a JVM or similar environment. I certainly don't begrudge the existence of a second implementation of Swift, although as a project maintainer, it does pain me a little to see that effort not going into improving the main implementation. (And I think SIL would help a lot with that efficient-value-semantics problem!)
But... a programming language is not just a grammar and a type system. There's a lot of room for variation between implementations, but basic semantics are part of the language, and that includes core library types. Many typical programs will not work the same way in the main Swift implementation and in Silver, and to me, that does make them not implementations of the same language. So, speaking just for myself, I'm not very happy about Silver calling itself a Swift implementation until it fixes that problem.