I think the Terra art, while posed similarly, is a big enough improvement that it might as well be a new artwork. (The Mickey one, on the other thing, looks like he modified the original only enough to change the outfit)
The pose is not, in fact, exactly the same, particularly in the arms. The Compilation of KH version has Terra's left arm hanging loose by his side and his right arm and Keyblade held defensively in front of his friends. The new version has both of Terra's arms stretched out at the same angle, which is kind of reminiscent of the stiff "T-pose"-esque pose he makes when fighting Xehanort in the Terranort body, and his Keyblade is held too low to be effective for defense [i]or[/i] offense. The overall effect, I'd say, is quite different: the original is confidently protecting his friends, the new version is surprised and unprotected.
Though I have to ask: where'd you get that version of the Terra art? Less of it is cut off than in the version linked in the first post (but it's not transparent...).