Hello, Reinhard!
Now, I obviously can't speak for Mike, but as an "innocent bystander", I didn't have the impression that Mike wanted to say that you are not welcome on the team. He simply gave an account of the x2go project state to the best of his knowledge.
I can see some bitterness and disappointment in your message, which seems to be partially caused by the fact that you feel no one else besides you has made substantial contributions to the Debian x2go packaging team, which, if it is true (I don't know how to check that, and will simply take your word for it), can be a frustrating experience. I've worked on projects where I was the lonesome cowboy or the last of the Mohicans or however you want to call it, and know the feeling, so I do have some sympathy for you there. ;-)
Also, you wrote:
However, it has still neither found their way to the designated git branches in collab-maint on alioth.debian.org, nor to the Debian archive. and I'd suggest to create a team PPA for the newly created x2go team in launchpad and move the packages there.
Again, I'm not a coder, so I can't jump in to help you directly - but maybe I can ask the proper questions to get this on the right track:
What, in your opinion, is needed to get going? What needs to be done? Which present list members could do it? Where do we currently lack resources that cannot be satisfied by list members (this should turn into a big "help wanted" on the home page)?
Kind Regards, Stefan