Yes and no.
The fact the core nodes have moved directory is because of the repackaging we did in 0.20.
The fact there are lots of node_modules directories is just how npm works.
Yes. /usr/lib/node_modules is the global npm module location - anything installed with -g as a global module.
You also then get locally installed modules - such as those you install just for node-red under /home/pi/.node-red/node_modules.
There are whole essays written about how npm lays out modules when running an install - I'm not going to go over it all, but here's the basics.
First thing to know is that when some code requires a module, it looks in the current directory for a node_modules directory, and looks in that directory for the module being loaded. If it doesn't find it, it moves to the parent directory and again looks for node_modules - and so on, all the way to the root of the file system.
Every module defines its own list of modules it depends on. One of the tasks npm has to do is to figure out how to install all of those dependencies.
In the early days of npm, it would install all dependencies below the modules own directory - so if you had module foo that depended on bar, and also module baz that also depended on bar, you'd end up with two copies of bar:
/usr/lib/node_modules/foo/node_modules/bar/
/usr/lib/node_modules/baz/node_modules/bar/
More recent versions of npm tries to reduce this duplication by installing dependencies as high as possible in the directory path. So you would get:
/usr/lib/node_modules/foo
/usr/lib/node_modules/baz
/usr/lib/node_modules/bar
However, if foo and baz depend on different versions of bar, npm hasto put individual copies of bar under the node_modules directory of the individual modules.
So yes you can end up with lots of copies of the same module installed; but npm does a lot of work to minimise that duplication.
