Project DREAM was created, initially, to better understand the complexity of the Borg's C-Consciousness, a small piece of it coming back along with the Eternity and several hundred surviving refugees saved at the battle of the Concord System (S02Ep12 Sons of Eternity). During the processing of these refugees it was deduced during psychiatric evaluations that some of them, when in REM sleep shared the same dream, more to that, they could interact with one another. At the time, understanding the C-Consciousness was at it's infancy, but Starfleet Scientists and Engineers were able to create one artificially with practices in understanding along with knowledge from the Liberated. This artificial C-Consciousness greatly expanded the abilities of these individuals and as further testing was done, eventually the individuals with the greater abilities were called The Dreamers.
Project DREAM, however, was not officially sanctioned even with these efforts as each time The Dreamers and those connected were within the Consciousness, able to affect it and change it, the reality created was never stable enough to be saved. The artificial C-Consciousness hadn't the capacity even as it's development grew as further science behind it was understood. It wasn't until Project DREAM discovered the locked persona, Calmest, within the mind of Owen Scott that Project DREAM hit a breakthrough. With their understanding of the C-Consciousness, the Calmest persona was extracted from, then, Commander Scott's mind, separating the two from one another. Calmest was a rendering agent, a program from the original Zahara reality on Ha'Dara (S02Ep10 The Saviors of Zahara). From the data the program Calmest provided, Project DREAM was able to create a stable branch of the C-Consciousness.