Moodle, the most popular open source LMS in the world has got more than 78+ million users allover the world.
According to the statistics on Moodle.net, at present there are more than 63k registered sites, from 222 countries all over the world and more than 78 Million registered users.
The top countries in terms of registration are as follows:
As far as the Moodle Version are concerned, the latest Moodle version i.e. 2.9 leads the numbers followed by the all time best Moodle 1.9.
For more details stats about Moodle LMS, please check out the original statistics at Moodle.net here: https://moodle.net/stats/
Please note that these statistics are dependent on the number of registered sites with Moodle HQ, you can also register your Moodle site by clicking the Site Administration > Registration link on your Moodle site to help improve the statistics.