I was searching for an answer to that same problem and found your post. After looking for a while, I decided to install the only available version of npm(server) I could find (4.2.something) using
zypper install nodejs-semver
After that, I chose to ignore dependencies while installing npm with zypper (solution 2). I used npm to install a module and had no problems at all.
The only difference is that I am on OpenSUSE 13.2.
Best regards