I think I have found the ancestor of the Hill People Gear Tarahumara.
Large vertical zipper opening
Similar side panel geometry
Designed to attach to larger packs
Single piece removable shoulder harness
(Apparently the newer version ditched the compression straps and went with a sewn-on harness)
Now I don't begrudge the Hill Brothers for borrowing from another pack, Even has often said that there is nothing new and that whether intentionally or not every designer borrows from those before them. He is also an admitted Osprey fan, and even refers to the front closure on their Ute pack as "Osprey style reverse pull." This just leaves me surprised that I'd never heard mention of this pack on their site or any of the many forums were the Tara has been discussed, they are certainly open about their inspirations and design process.
HPG certainly has nothing to hide, they have added so much that the capabilities of these two packs can hardly be compared, they added a beefy compression system, a fuller harness, dual water bottle pockets, and a host of other features, so this is not an "I caught you!" post so much as an observation on how much borrowing happens in the design world.
Found another backpack in the same genus while flipping through my old Backpack magazines, the Mountain Hardwear Riff:
and another, this time the Lowe Alpine Moab. bottle pockets but no compression straps.