The story of JAU is based on the X-Box360/PS3 version of TFU, but it will be expanded.
All in all it will be a longer story than in the original TFU. More things will happen, but we'll always try to keep it as canon as possible because we're not just only building a "mod", but we're building a "Star Wars Mod"!
You won't meet Luke Skywalker or Han Solo, because many dialogues of the "Original Trilogy" wouldn't make sense anymore.
You guys should make alot of the dialoges of the original trilogy make sense!
I think they don't have to!
Their idea isn't compatible with the original triologie, so in my oppinion its very interesting and I think they'll have much more latitude to create a new story without using the TFU-ending.
I don't know if you liked the both endings of TFU, but I think they were disappointing... :(