LG bought source code... That's Legacy. You don't buy Open Source, you just use it and contribute back to it. Or fork it off and run proprietary after you build up some independent code.
So there is something in Legacy that LG needs to complete their vision of a smart TV.
They own Legacy webOS, right?
Their TV will need Apps. I'm sure they see a revenue stream in placing new Apps in HP's App Cat (HP still owns/controls that) maybe for 3.x at least.
If there is any filter down from LG projects to Legacy devices that would be a) very good news for us and b) very smart of them as it brings current users into the LG camp and builds brand loyalty.
I would guess they plan Apps that will be backward compatible with Legacy, but would not expect any OTA updates to any Legacy Hardware OS from LG...