I’m somewhat confused: could the OP and others who commented here clarify why this is suddenly a (new/recurring) topic? Or what has changed wrt ROS 1 that makes this a concern (chances are that ROS 1 uses / has reimplemented technology which is patented, either directly or one of its dependencies)?
Is there something different about how DDS and its implementations treat licensing from other software products / OSS offerings?
Sufficiently different that we need “clarification [on] the legal situation”?
You’re asking for DDS vendors to essentially give away their software for free, correct?
There are already quite a few “free” DDS implementations (free as in: from a licensing perspective), the one shipped with ROS 2 by default being a good example. It’s even Apache-2.0 licensed. Adlink Vortex is Apache 2.0, RTI has a community edition of their implementation. Several other vendors have similar offerings.