With help from echicken I got my reCaptcha working for new users.
In newuser.inc I used the standard form from reCaptcha.
In newuser.ssjs , right above the Validate date comment/section:
/*Validate Captcha*/
 if(http_request.query["recaptcha_challenge_field"] != "") {
  load("http.js");
  var response;
  var http;
  var captchaChallenge="&challenge="+http_request.query["recaptcha_challenge_field"];
  var captchaResponse="&response="+http_request.query["recaptcha_response_field"];
  var captchaIP="&remoteip="+http_request.remote_ip;
  var captchaPrivateKey="&privatekey=yourprivatekey";
  // Create HTTPRequest object 'http'
  http = new HTTPRequest();
  response = http.Post(
    "
http://www.google.com/recaptcha/api/verify",
    captchaChallenge+captchaResponse+captchaIP+captchaPrivateKey
  );
  //print(response);
  if(response !== "true\nsuccess" ) {
    err=1;
    template.err_message+="Bad captcha\r\n";
    template.errs["captcha"]="Captcha is incorrect.";
  } /*else {
    err=1;
    template.err_message+="Good captcha\r\n";
    template.errs["captcha"]="Captcha is correct.";
  }*/
 }
---
 þ Synchronet þ Digital 52 BBS - digital52.com