They appear to Luke as they knew him. Good, that makes sense.
The Lucas change to Jedi, as it appears in the re-releases:
Wonderful. I can just picture Lucas seeing this as a masterstroke to tie in all of the movies.
But let's think about this from Luke's perspective:
Luke: "Oh, hey. I'm so glad my two teachers old Yoda and old Obi-Wan showed up. It shows that they are always watching over me. But wait... who's that random young guy? I don't recognize him. Is that like an alternate version of me as a Jedi knight or something? Oh well, wish dad could have been here."Never made sense to me story-wise.
This cartoon from the folks at How It Should Have Ended did a nice job illustrating this point, while making some other funny changes.
That "You killed all of us as children" line gets me every time.