This week's book giveaway is in the Reactive Progamming forum. We're giving away four copies of Reactive Streams in Java: Concurrency with RxJava, Reactor, and Akka Streams and have Adam Davis on-line! See this thread for details.
Joomla and Drupal are both Content Management Systems (CMSs). I can't speak for Joomla, but I do know that Drupal is a consumer of CMIS. That means it can easily create, query for, update, and delete content that resides in a CMIS-compliant server. Using CMIS is a very common approach for integrating Drupal and CMIS servers like Alfresco.
These systems could also be CMIS-compliant servers, but someone would have to do that work. They are not CMIS providers out-of-the-box.
This looks like a job for .... legal tender! It says so right in this tiny ad: