Koha
Koha is an open source/FLOSS library management system (under a GPLv3 license) with a very active user and development base.
According to its website, Koha is
built using library standards and protocols such as MARC 21, UNIMARC, z39.50, SRU/SW, SIP2, SIP/NCIP, ensuring interoperability between Koha and other systems and technologies, while supporting existing workflows and tools. (Koha: About)
Koha's (gitea-based) Git repository is accessible at: https://git.koha-community.org/koha-community/koha and mirrored to GitLab.
The Thoth Wiki has been developed in the context of the COPIM (Community-led Open Publication Infrastructures for Monographs) project. Individual contributions to the wiki have been made by Tim Elfenbein, Rupert Gatti, Ross Higman, Vincent W.J. van Gerven Oei, Tobias Steiner and Hannah Hillen under the general editorship of Van Gerven Oei. All data are available under a CC-BY 4.0 license.