Could be download the source code a application from (npm.org) without using the npm install xxx?
This is because I need a package that is not in github but got an error when installed with npm install, downloading it file have an error.
You can use npm view [package name] dist.tarball which will return the URL of the compressed package file.
Why don't you create an empty directory outside your project, do an npm install there, and get the source from node_modules.
cd /tmp
mkdir dir1
cd dir1
npm install intersting_module
cd node_modules
the full module is right there.
You could also go on http://npmjs.org, look for the module there. Most modules will list there repository and you can get the code from there.