Debian has decided to create two logos: one logo is for official Debian use; the other logo falls under an open use type license.
However, it later contains:
It could be said that Debian has a single logo in the sense that "the" (open use) logo is included in all logos. In that sense, all logos could be considered as versions of a single logo. However, considering that we use the terminology "Debian Open Use Logo" / "Debian Official Use Logo", I recommend that we stick to the terminology according to which we have 2 logos. The above paragraph could be changed to refer to "The Debian logos" or to "The Debian swirl" (which would have the advantage of indicating that the logo is a swirl). The open use logo's description refers to the 2 versions of each (open/official) logo as "flavors".
The status of the official use logo is being discussed: https://lists.debian.org/debian-project/2012/10/msg00002.html