The Eclipse Cyclone DDS project (https://github.com/eclipse-cyclonedds/cyclonedds) at long last has received an RMW implementation, which can be found at https://github.com/atolab/rmw_cyclonedds. Eclipse Cyclone DDS is an Eclipse Foundation project and so a true open-source implementation of DDS. That it has excellent performance as well hopefully makes it a rather attractive proposition
I’m hoping that this RMW layer will eventually be accepted as a ROS2 package, move to the ROS2 repositories and become part of the set of packages that is built by default, but until then, it’ll be available in this location. Also, it is really still very young, so please test the hell out of it and then be gentle with me when you report the issues you will inevitably encounter …
To build/use it you need to have a recent commit of Cyclone DDS installed somewhere, say in $CMAKE_INSTALL_PREFIX. Actually building the RMW implementation then follows the standard procedure: clone it in a ROS2 workspace source directory, set CycloneDDS=$CMAKE_INSTALL_PREFIX/share/CycloneDDS and build with colcon as usual.