Installing Node.jsI've downloaded the sources for Node.js from http://nodejs.org/#download. It compiled (configure+make) and ran without any problem.
The scriptThe following script contains a class handling a GeneticCode and the server TranslateDna translating the DNA to a protein, it handles both the POST and the GET http methods. It no parameter is found it displays a simple HTML form, else the form data are decoded and the DNA is translated. The protein is returned as a JSON structure.
Running the server
Server running at http://127.0.0.1:8080
> curl "http://localhost:8080/"
<html><body><form action="/" method="GET"><h1>DNA</h1><textarea name="dna"></textarea><br/><input type="submit" value="Submit"></form></body></html>
> curl "http://localhost:8080/?dna=ATGAACTATCGATGCTACGACTGATCG"