B2 / cafelog, more commonly known as b2 or cafelog, was the ancestor of WordPress. B2 / cafelog is estimated to have been used on approximately 2.000 blogs by May of 2003. It was written in PHP, and used MySQL. The project developer Michel Valdrighi, is currently contributing to WordPress.
Although WordPress is the official successor of b2 / cafelog, b2evolution continues to grow.
The b2evolution is a Content Management System (CMS) that aims to easily create and maintain web pages for information exchange.
It can be used as a simple homepage on a blog, photo gallery or newsletters ... up to a complete community site with a forum, a directory of members and private messages.
B2evolution includes everything you need in a single integrated package.
WordPress now introduces 2003 as a joint effort between Matt Mullenweg and Mike Little to create a b2 fork. The WordPress name was suggested by Christine Selleck, a friend of Mullenweg.
WordPress is free and open source software used as a publishing platform from blogs. And WordPress is written in PHP and MySQL. It has many features, with an architecture that allows additional features.
As mentioned before, it was released for the first time in 27 May 2003, by Matt Mullenweg as a variant of b2 / cafelog.
So at 27 May 2018 will have 15's birthday on the popular platform.
* with information from Wikipedia