I used https://reporeq.apache.org/ to request a new Git repository for Cayenne Modeler and the tool said it would be created at https://git-wip-us.apache.org/repos/asf/cayenne-modeler.git.
I also opened a Jira with Infrastructure to see if we can do an import of the current code at https://issues.apache.org/jira/servicedesk/agent/INFRA/issue/INFRA-13223. mrg