Zsh was never part of a commercial Unix, so I suspect you are thinking of Ksh. As far as I can tell, Zsh has always been free software: the earliest version I

Zsh was never part of a commercial Unix, so I suspect you are thinking of Ksh. As far as I can tell, Zsh has always been free software: the earliest version I could find used the GPL, but it now uses something more MIT-like. Bash is probably more widely used because it was available earlier than Zsh, and because it was the "official" shell of the GNU project (better marketing).