"LzHTTPDatasource#doRequest(..)":

There's one obsolete if-clause, as "if (q.length > 0)" is always true, because "q" will have at minimum a length of "1".
[code]
var q = '?'

...

if (querystring != null && querystring.length > 0) {
  if (q.length > 0) {
    q += sep + querystring;
  } else {
    q = querystring;
  }
}

...
[/code]

So we can say:
[code]
...
if (querystring != null && querystring.length > 0) {
  q += sep + querystring;
}
...
[/code]

---

Second issue:
If we have got a question mark in the url, we must say "q.substring(1)", or else we'll have got two question marks in our final url, as "q" starts always with a question mark.
[code]
var q = '?';

...

var url = this.src
if (q == "?") {
  // don't add empty args list
} else {
  // if there are already query args in the url, separate them with a '&'
  if (url.indexOf('?') >= 0) {
    url = url + "&" + q;
  } else {
    url = url + q;
  }
}

...
[/code]

So this should be:
[code]
...
var url = this.src
    if (q == "?") {
        // don't add empty args list
    } else {
        // if there are already query args in the url, separate them with a '&'
        if (url.indexOf('?') >= 0) {
            url = url + "&" + q.substring(1);
        } else {
            url = url + q;
        }
    }
...
[/code]