JavaScript has a lot of other advantages, if you stop and think about it.
A. Security is a non-issue with JavaScript; it's built into the language.
Even though the AI is dangerous, it is only dangerous if it grows and multiplies and takes over the world -- which it is not going to do in its JavaScript incarnation.
For AI in JavaScript to become dangerous and a threat to human primacy, something like the following outlandish and far-fetched scenario would have to take place. First, highly skillful and ingenious programmers would have to take notice of the JavaScript AI floating around the Web. Then the world's best programmers -- who are already extremely busy -- would have to perceive some sort of intellectual and bragging-rights challenge in taking apart the JavaScript artificial intelligence and putting it back together again with enhanced capabilities and genetic traits likely to ensure the survival and success of AI entities in the brutally Darwinian jungle that is the World Wide Web, no thanks to TimBL.