You can build a node variation of this library using build/build.js : the resulting package will be in build/node.
Without cloning this project you can use it directly using npm : npm install proj4js
In your JS : var Proj4js = require("proj4js");
var Proj4js = require("proj4js"), proj = new Proj4js.Proj("ESPG:2154");
console.log(Proj4js.transform(Proj4js.WGS84, proj, new Proj4js.Point([45,5])));
For more documentation on Proj4JS usage, please read the original proj4js documentation : http://trac.osgeo.org/proj4js/
git clone git://github.com/temsa/node-proj4js.git cd node-proj4js cd build node ./build.js cd node # here is the resulting package !
then you can use it with npm link (see documentation) or do a npm install