The Nuxeo documentation says 'Nuxeo DAM' addon does not require registration. But while installing via nuxeoctl it errors out that its not registered.
Relevant document: https://doc.nuxeo.com/nxdoc/nuxeo-add-ons/
Nuxeo home: /NuxeoOpenSource/nuxeo/nuxeo-distribution/nuxeo-server-tomcat/target/nuxeo-server-tomcat-10.2-SNAPSHOT Nuxeo configuration: /NuxeoOpenSource/nuxeo/nuxeo-distribution/nuxeo-server-tomcat/target/nuxeo-server-tomcat-10.2-SNAPSHOT/bin/nuxeo.conf Include template: /NuxeoOpenSource/nuxeo/nuxeo-distribution/nuxeo-server-tomcat/target/nuxeo-server-tomcat-10.2-SNAPSHOT/templates/common-base Include template: /NuxeoOpenSource/nuxeo/nuxeo-distribution/nuxeo-server-tomcat/target/nuxeo-server-tomcat-10.2-SNAPSHOT/templates/common Include template: /NuxeoOpenSource/nuxeo/nuxeo-distribution/nuxeo-server-tomcat/target/nuxeo-server-tomcat-10.2-SNAPSHOT/templates/default Optional dependencies [nuxeo-web-ui, nuxeo-jsf-ui] will be ignored for 'nuxeo-dam-6.4.1-SNAPSHOT'.
Dependency resolution: Installation order (1): nuxeo-dam-6.4.1-SNAPSHOT Packages to download (1): nuxeo-dam:6.4.1-SNAPSHOT
Do you want to continue (yes/no)? [yes] yes Downloading [nuxeo-dam-6.4.1-SNAPSHOT]... Aborting packages change request
Failed commands: * download (nuxeo-dam-6.4.1-SNAPSHOT) Registration required.
What documentation page are you talking about? Please include relevant links when your report a problem.
Downloading some precompiled package from the Nuxeo Marketplace servers requires registration, as it's a service that Nuxeo provides. Note that SNAPSHOT versions of the packages are not available from Nuxeo Marketplace.
You can always compile this software yourself of course.