The first version of the Debian-based Ubuntu, named "4.10 Warty Warthog", was released on October 20, 2004.[52] Because it was distributed as a free download, it became one of the most popular and successful operating systems with more than "40 million users" according to Canonical Ltd.[53][54] However, Murdock was critical of the differences between Ubuntu packages and Debian, stating that it leads to incompatibilities.[55]