It's easy to brag about how many languages your only-works-on-our-highly-customized-server application uses. What about an application meant to run on lots of computers for use by ordinary users.
I present to you the application I love to hate: lilypond
- lilypond's own music typesetting language
- c++
- guile
- postscript
- tex/latex
- python
- shell/make
- metafont
- vim scripts, emacs lisp scripts
- texinfo
- html/css
- flex
Count the paradigms too: traditional, functional, stack-based, scripting, declarative, and various specialized languages.