Since 2002, over 400 individuals (including some representing organizations) have contributed source code to Tiki.
List of people that had commit access via SourceForge (used from the beginning of the project in 2002):
http://sourceforge.net/p/tikiwiki/_members/
And GitLab progressively became the main repo in 2019-2020. Please see: Tiki Version control history
https://gitlab.com/tikiwiki/tiki/-/project_members
See also: https://www.openhub.net/p/tikiwiki/contributors?sort=commits
Commit stats are updated with each release and can be found in the copyright.txt shipped.