[dominicl]

IMHO the differentiator is deeper yet everywhere engrained in OTP/Behaviours and the famous "Let it crash" slogan. It is the OS-Style process and resource isolation. That is something you can't port with a library into a language that doesn't have it built-in. Lightweight processes, are not the same if they can crash each other, or messup some shared objects/resources/...

You can implement actor behaviours in go or node or even c, but without that lower level support it will never give you the stability guarantees that Erlang process isolation is giving.

To draw a weird comparison Elixir (with Erlang process isolation) brings two world together. First it's a PHP/Ruby level of fire-and-forget productivity because each http request is handled in an independent isolated process, which if it crashes won't affect the system, but instead provide automatically a nicely debuggable crash log. And second it provides natively all distributed tools for long-lived systems. E.g. PubSub , Sessions and database connections don't have to be rebuilt like in ruby/PHP on a per request basis but can be their own long-lived processes.

If there would be a library that could bring this easy to use process isolation+communication e.g. to C programming it would be a game changer. But the best you get in all other languages I'm aware of is to use actual process isolation (fork multiple node/ruby/go processes) and then use some kind of IPC manually or redis or k8s...