6 most popular alternatives to opencmis: apache-chemistry, ecm, nuxeo, activiti in java; dotcmis in c#; pygraphviz in python;
try to look at graphofknowledge.appspot_dot_com or here g2.com/products/apache-chemistry/competitors/alternatives
There is an open-source Java-based (Spring Boot) "OpenCMIS" sponsored by Alkacon Software. It's not obviously related to Apache Chemistry OpenCMIS but it has seen maintenance within the last 6 months or so.
It's also available in Docker Container form, which is nice for quick deployments.
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