linuxmemes

Not necessarily. For all of these cases, Debian, Ubuntu, Pro, the community and Canonical are package maintainers. Implementing patches means means one of: grabbing a patch from upstream and applying it to a package (least work, no upstream contribution); deriving a patch for the package from the latest upstream source (more work, no upstream contribution); creating a fix that doesn't exist upstream and applying it to the package (most work, possible upstream contribution). I don't know what their internal process is for this last case but I imagine they publish fixes. I've definitely seen Canonical upstreaming bug fixes in GNOME, because that's where I have been paying attention to at some point in time. If you consider submitting such patches upstream as actively involved in project development, then they are actively involved. I probably wouldn't consider that active involvement just like I don't consider myself actively involved when I submit a bug fix to some project.