DW Weekly quotes this Lubuntu developer blog post, which quotes the following comment by Mark Shuttleworth:
Thanks for the great work and progress of Lubuntu in the past 2 years. The fact that you are now 100% in the archive, and using PPA's and other tools effectively, makes it possible for us to consider recognising Lubuntu as an official part of the project. ... From my perspective, I see no problem in providing Lubuntu with the means to book sessions at UDS, and for us to call attention to Lubuntu in the project release notes. ... Our goal with Ubuntu is to ensure that the archive contains the full richness of free software. LXDE is definitely part of that, and with the other desktop environments making greater demands on PC resources, LXDE has a continued role to play.
DistroWatch Weekly, Issue 403, 2 May 2011