>Now I'd like to be able to exececute that script from within another JS script. Can I do this?

If you would like to execute a specific function from that script, then, you may just call the name of the function as is.

If it is in regards to include a script from another included script, I always moved away from such design as I believe all included scripts should be part of the main page.

I'm not sure if you can include a script from another script. If it's not easily possible, maybe you can try the document.write() approach to include the HTML line to include the script. Then, maybe a call to the related function name would do it.