I just checked, and it seems the interesting parts can actually be reached over rsync:
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R S Y N C . O S U O S L . O R G
Oregon State University
Open Source Lab
Unauthorized use is prohibited - violators will be prosecuted
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...
ros The Robot Operating System (ROS)
ros-main The main ROS debian package repository
ros-testing The testing ROS debian packages repository
ros2-main The main ROS2 debian package repository
ros2-rhel-main The main ROS2 RHEL packages repository
ros2-rhel-testing The testing ROS2 RHEL packages repository
ros2-testing The testing ROS2 debian packages repository
ros_docs_mirror
ros_wiki_mirror
...
We’ve just started syncing ros2-main (already had ros-main).
(related discussion: Can we fix rsync for packages.ros.org)