Consider: (1) it's essentially impossible that no one involved had ever heard of the Gnome desktop (it's the top result when I search for "gnome" on Google); and (2) after being contacted by the Gnome Foundation, Groupon filed even more trademark applications.
There are a lot of decent, hard-working hackers at Groupon, and quite a few of them, I'm sure, regularly visit HN. They won't be happy to find out about this.
Are there any Groupon insiders here willing to comment on this, maybe anonymously?
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UPDATE: Groupon just released an official response: https://news.ycombinator.com/item?id=8590343 -- they now say they will be "glad to look for another name." If they really mean it, kudos to them for changing their position!