Using Fedora 20, `which ksh` returns nothing. I would think people wanting to adopt a language like this are more likely to be using Linux 2.6 than AT&T UNIX, but I would suspect you're wrong about which one is now more prevalent now anyway. I can't remember the last time I used a *nix box that didn't have bash (or a VERY similar shell) installed by default, and this is certainly a huge step up over having to write both batch and bash independently anyway.