With projects like Mathics[1], that aim for Language compatibility with Mathematica, on the horizon it makes sense to want to separate the language from the implementation.
Seeing this post hit HN just a few days after Mathics gave me a paranoid feeling. Why now? Is Wolfram feeling the heat and looking for a new trademark to deny his competitors?
And Mathematica 9 just came out, so maybe it was Mathics feeling the heat! Despite the vacuum-like nature of our internal HN-eval-post loop, the rest of the world isn't standing still. It's actually a little surprising that they're only talking about this now, given how long Mathematica has been around.
I understand that this makes sense for Mathics. What I don't understand is why Wolfram has any interest in separating the language from the implementation.
It's worth noting that the developer of Mathics joined Wolfram recently. Might be related...