It's good to have a timetable, but that doesn't mean it's going to happen. September is 8 months away, and a lot can happen in that time. WebOS might be sold, or HP might have rush of brains to the head and figure out how to produce decent tablet. (Stranger things have happened.)
And today HP also took the first step towards the goal of releasing webOS under an open source license; they've released another part of Enyo under an open source license.
Enyo is the app framework that TouchPad and webOS apps are built on. HP had already released Enyo 1.0; today they added Enyo 2.0 Core. The earlier version of Enyo is the basis for the native apps on the TP and webOS devices (including both HP's apps and
thousands hundreds dozens of third-party apps), and Enyo 2.0 Core adds support for other web browsers (Firefox, IE, Chrome, etc). HP said that this will enable webOS apps to run better on other mobile platforms. I don't know why you'd want that; Android, iOS, OSX, and Windows don't need any more apps.
I bet you're wondering about the license. According to HP, you can download Enyo under the Apache 2.0 license. I don't have the technical knowledge to tell you the ins and outs of that particular license, but it's good news nonetheless. I half expected HP to invent their own "open source" license which might have neglected some of the key ideas in open source.