Seeing as this was built by the creators of MuPDF [1], I'm guessing they built this because they need to use JS to support embedded JS forms. 1: http://www.mup

Seeing as this was built by the creators of MuPDF [1], I'm guessing they built this because they need to use JS to support embedded JS forms. 1: http://www.mupdf.com/ http://www.mupdf.com/ (artifex)