It's WDP 8102 with a bumped 8xxx number. Nothing more according to all of the contributors indicating such.
If you are talking about the thing on connect. It's nothing but an online setup version of Windows Developer Preview. It is 8102 (WDP 2011 build)
I have heard of one difference(but I have not tried it myself): You can't upgrade from win7 to WDP using the install ISO from MSDN(install.wim); but you can do that using the web installer(install.ESD).
The could have done the online installer test with Windows 7 too, but they decided to do it with the Windows Developer Preview which is obvious since the online installer will be for Windows 8 and not Windows 7.
You can update Win 7 to WDP using the online installer, I did it during the "Fair". You could also make a bootable USB to install WDP on a different partition, I did this too.
If you guys talking about how the build number gets bumped up after installing some updates on WDP, it's hardly worth noting. Everybody gets that "bump up". That happened the week or so after WDP was released, nothing new lately. The build that you download during the Install Fair is identical to the WDP build released.. same exact build number and also gets "bumped up" after updating it.. as expected since it's the SAME. And there is NO way MS is gonna release beta so close after WDP, so while they are preparing it, it ain't gonna leak anytime soon and will be public anyway when it's done.
I and asfaltas were talking about build 8131 and I thought mikedl was answering to that only. But it seems mikedl did not get asfaltas. He thought asfaltas is talking about build 8102.
Yeah, that's what I thought. About asfaltas question, yes I guess it should be B1, because in canouna's screenshot of a earlier build(shown in the OP), it already displayed B1.