Well, you asked 2 things. The first question is an abolute figure which is difficult to find out. If people download GL they may not necessarily use it but maybe only test it.
Quote by mugen: Hi, does anyone know how many websites are using the Geeklog CMS?
The second question is a relative figure e.g. in %.
Quote by mugen:
Which CMS (geeklog, joomla, mambo, post-nuke, etc.) has the most users at this time?
So it is just an idea if you count all the downloads of Mambo, Drupal, Geeklog (if these figures are available) you could say they are 100% and calculate the share of each of them.
The absolute figure doesn`t tell you much anyway. I suppose you want to know which CMS is most popular.
The same is true for the links you find on google. So find a wording that is typical for geeklog only. It is not the word geeklog. It is rather a combination like "Copyright powered by Geeklog".