As part of its efforts to promote a unified Android platform, OHA members are contractually forbidden from producing devices that are based off incompatible forks of Android.
With the benefit of hindsight from October 2014, the OHA turns out to have been an initiative without visible value. There is no public process for providing input and guidance to Google for future features desired in Android. The OHA doesn't issue any roadmaps, or indeed any announcements at all. Some people speculate that the purpose of the OHA is give Google the cover of an industry consortium, while all the key decisions are actually made in the Googleplex.
At the same time as the announcement of the formation of the Open Handset Alliance on November 5, 2007, the OHA also unveiled Android, an open sourcemobile phoneplatform based on the Linux kernel. An early look at the SDK was released to developers on 12 November 2007.