Microsoft's COM shows that you don't need any magic features in your language - just regular late binding for functions. You can interface with COM components - the one mainstream implementation of what this article is describing - in programs written in C. Because underneath, the whole thing works by asking the OS to give you an array of function pointers in exchange for a UUID.
I'm familiar with COM and I do think the kind of interoperability you get with open multiple dispatch is of a different character altogether. There has not been any theoretical reason why this has to be true yet, but empirically it has been surprisingly powerful in Julia. I guess Common Lispers would relate to it too.
