@TheEvilSkeleton @linuxmint @nekohayo
I have no horse in this race but it seems to me that the Mint dev was reasonable. He explained the same issue exists in Debian and Ubuntu (i.e. the About dialogue links to the Gnome Calendar repo) and he offered to patch the dialogue in Mint.
You then said you weren't interested in the "intricacies" and repeated your demand that they fork Calendar. I get your frustration but I understand why they closed the issue.