Mortgage Loan Calculator Plugin ???

I am using the following mortgage calculator plugin for my site.

https://www.ads-software.com/extend/plugins/mortgage-loan-calculator/

After installing it, I noticed that java scripts, images, css are all imported from the plugin developer site and are not getting installed locally on my site. Is it safe to use pligins that import java scripts and related CSS from the remote plugin developer site? What is the remote site goes down and or the site changes the java script???

Any advise ???