"Arguably the most deployed Lisp today?" That's an interesting question. My other guess would have been Gimp, and based on a quick glance at Debian's popcon,

"Arguably the most deployed Lisp today?" That's an interesting question. My other guess would have been Gimp, and based on a quick glance at Debian's popcon, I'd say Gimp might be slightly in the lead. Then again, like Open Firmware deployed Forth on millions of computers, right under our noses, it would not surprise me at all if there were a simple Lisp implementation hidden on every computer in the world. Is there anything more recent than DSSSL?