In October 2014, when the original CatBlock extension was officially discontinued by Michael at AdBlock, and open-sourced under the GPLv3 license by AdBlock Team, Kieran and Tomáš (at that time members of AdBlock Team), decided to keep CatBlock alive independently. Kieran & Tomáš left the AdBlock team in early 2016 to put more effort into development of CatBlock, including creating versions compatible with both Mozilla Firefox and Microsoft Edge. For more information about the development & history, please check out https://github.com/CatBlock/catblock