“u” is the front liner of the branding in the Ubuntu family font and of the official brand; in a philosophical approach a pointer towards humanity (as in unity)
the symbol itself, comprised of two pieces formed together, expresses the same idea
both symbols are closely related, placed, and in their union accomplish their purpose of expressing both the philosophical and material aspects of unity via Gestalt
There was some discussion on the Ubuntu GNOME mailing lists about somebody selling Ubuntu GNOME for $30. One of the follow-up emails was from Patrik Bubák, an Ubuntu GNOME dev, who said:
As far as the logo is concerned, borrowing GNOME's was a mistake from
day 1. It's highly confusing, and due to its complexity difficult to
work with, plus using someone else's logo as our own isn't quite all
right, even though certain permissions have been given it will never
be clear unless it's completely changed, which it will, soon.
Best Answer
This one?
The new logo is a combination of the letters U and G.
I found a topic on the ubuntu gnome artwork mailing list pointing to the project page: