ubuntu open source ... think again

i was at ubuntuforums.org and observed a very thing .... which as far as im concerned goes against their OSS belief ... please dont get me wrong here but its funny that a company which promotes open source actually uses a closed source software ... vbulletin

why arent they using the open source phpbb? do they actually believe in their OSS concept or they believe like most windows user ... use what does the work best whether oss or closed source

not a fight just a question