This database is based on AtoM software. AtoM stands for Access to Memory. It started as a project of the International Council on Archives with the aim to provide the international archival community with a free, open source software application to manage archival descriptions in accord with ICA standards. It is easy to use, multilingual and fully web based, which allows institutions to make their archival collections available online.
You can learn more about AtoM here: https://www.accesstomemory.org