Well, not exactly. From wikipedia: "Node.js consists of Google's V8 JavaScript engine, libUV, and several built-in libraries." So node installs a version of the V8 engine in your dev environment, so it can run js on the server without a browser.
That's why jam requires node - it's written on javascript and uses node packages so it can work with the filesystem, and do other server/dev environment things that js in a browser can't do.
When you develop with node, it's just like doing development for any other language.
Edit: in case this wasn't clear - you aren't working in a node environment. In this case, node is simply used because it can execute javascript in a server environment. So jam can be written in js and do filesystem stuff if it runs using the node utility. Jam simply runs on node, but a project using jam doesn't necessarily need to be a node application.
Thanks for that explanation. One last question: why would you do 'jam install backbone'? Are people developing all their client-side code in the node environment as well?
[Or, it seems like maybe node in this case is just a dependency for jam, which is simply a tool used to make all your JavaScript development easier, without introducing any extra runtime dependencies.]
There are two sides to Node. One is the HTTP server environment you're thinking of. The other is just as a generic JavaScript execution environment, with packages for filesystem etc..
That's why jam requires node - it's written on javascript and uses node packages so it can work with the filesystem, and do other server/dev environment things that js in a browser can't do.
When you develop with node, it's just like doing development for any other language.
Edit: in case this wasn't clear - you aren't working in a node environment. In this case, node is simply used because it can execute javascript in a server environment. So jam can be written in js and do filesystem stuff if it runs using the node utility. Jam simply runs on node, but a project using jam doesn't necessarily need to be a node application.