[skrebbel]

Integration, ecosystem, exit strategy.

Integration so that you can easily integrate new Smalltalk code (in this case) with existing JVM code that your organisation/product might have.

Ecosystem because you don't need to kickstart a massive community of developers, open source libraries, a standard library, and so on, to have a useful language. Basically, by making a language that targets an existing platform (such as the JVM, CLR or JavaScript), you're "batteries included" from the very start. Better yet, the batteries will be familiar to shares of developers. This is major. Ever wondered why Lisp was only used by a couple of men with beards (and pg) until Clojure? I can promise you, it wasn't the square brackets.

Exit strategy because you want to be able to get out as easily as you got in. If you build non-hobby software with Redline Smalltalk, and for whatever reason the whole thing blows up in your face (e.g. big performance or security problems, project ends up unmaintained with large nuisances, and so on), you can migrate code to another JVM language bit by bit.

[pron]

True, and I would also add the best performance of any managed runtime and the best profiling of any runtime.

Unless your language's main features coincide with the very specific pain points poorly addressed by the JVM (like struct arrays or mobile-phone deployment), I'll say that the JVM is the default target choice. It is any other choice that will need to be justified.

[supar]

I could say exactly the same for any source-to-C compiler, and/or any system allowing decent FFI with C. Unless there is some different reason than the JVM itself, C has an even larger code base.

[skrebbel]

In a way, C can be considered an "existing platform" in much the same sense. I didn't include it in my list of examples because I really don't want to have to fight build tooling and cross-platform dependency hell in 2012 if I don't absolutely have to. With e.g. the JVM, you can get a jar from somewhere (or maven it in), and -poof- it just works, everywhere. This is a major advantage to the whole "ecosystem" point.