If you have a web server, you can easily copy the Javascripts (they are all checked in to the GitHub repository) to an accessible path on your server, and then you need to modify the OpenSprinkler source code to point to your server. The path is defined in this source file:
https://github.com/rayshobby/opensprinkler/blob/master/OpenSprinkler%20Controller/software/libraries/OpenSprinkler/examples/interval_program/interval_program.pde
notte the JAVASCRIPT_PATH variable on the top. This should be a simple change, but it does require re-compiling the source code.
I will consider adding an configurable path in the options in the future. At the moment it’s tricky to add because the current program has pretty much maximized the program memory space.