Calling custom phonegap plugin gives error "Uncaught ReferenceError: calendar is not defined"

Calling custom phonegap plugin gives error "Uncaught ReferenceError:
calendar is not defined"

I am creating a phonegap test project with custom calendar plugin
published here. When I call it on device ready, I get "Uncaught
ReferenceError: calendar is not defined" error. I have published the code
on github. Here's the link if you want to take a look. Thanks in advance
for help.