You can clone with
HTTPS or Subversion.
(this will show up more as people continue upgrading to 0.10.x)
as an old example which was discussed in irc recently:
npm show commander version reports 1.1.1 while npm install commander installs 1.0.3 on systems that have node version 0.4.x (since the engines line was updated to 0.6.x after 1.0.3 and before the next release)
npm show commander version
npm install commander
The engines field was made purely advisory quite a while ago. This will stop being a problem as people upgrade to at least 0.8.