Creator of DevOps & Node.js contractor in London. •

…is Clojure, LFE etc, i.e. implementations of Lisp running on top of popular virtual machines. There are two advantages to this approach:

  1. You get a lot of libraries for free, as long as the author spent a bit of time thinking about interop.
  2. (new) Lisp code can live side-by-side with (older) Java, Erlang &c code. There is no need for a radical rewrite or any interop difficulties — you simply write parts of your system in Lisp where it makes sense, perhaps gradually replacing older non-Lisp code.

This would also mean that:

Common Lisp is not going to get mainstream for three reasons:

  1. It’s full of what looks like cruft to beginners.
  2. It’s not straightforward to get started with. Advising newbies to learn Emacs & SLIME is not wise and doesn’t work. Choosing an implementation to start with can be tricky too.
  3. The community is not making an effort to make CL seem cool.

PLT Scheme is not a contender either, because it’s perceived as little more than a Lisp for teaching, which isn’t true, but the community isn’t doing much to shatter this perception.

Update discussion over at Hacker News