Open-source software is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, improve and at times also to distribute the software.
The software I use is generally Open Source software. This site runs on Joomla and my genealogy software which generates the family section for registered users, is Gramps, displayed within a section of the site. Wordpress I use on other sites, one of which is a sub-domain here about Open Source software, which is here Wordpress section or just click on the designBethan logo below in the footer to go to my other main Wordpress site.
More on these three are on the sub-menu's.