Source-sans-pro:n2:default.js’ is a remote file cannot be edited

Which version of Dreamweaver?  Help > About Dreamweaver.

That is expected behavior given that the font is remotely hosted on Adobe's servers. 

What are you trying to do exactly?

More information about what you are doing when this error apepars vs what you expect to happen would be helpful.

If you're using a link as Ben illustrates, and are trying to make a change to the Source-sans-pro:n2:default.js file, it'll never work.

The error would mean DW can't modify the file because it is not within your local site folder.

Did you use 

<script src="https://use.edgefonts.net/source-sans-pro:n2:default.js" type="text/javascript"></script>

I.e. https and not http?