Re: Relationships and Pairings
FT characters in general don't strike me as being the type to hold grudges. I think it was mentioned most of them had troubled pasts so I don't think they would be the type to judge others for their past or mistakes. That said, it is quite obvious he is helping levi because he feels bad about what he did to her.
Well, Jet and Droy held a grudge, and Levy was fearful of him, but didn't hate him. Then Gajeel let Jet and Droy beat him up, and he protected Levy from a stray shot from Luxus. After that Jet and Droy pretty much went "apology accepted" and Levy mostly stopped being fearful of him. Her fears seem to be forgotten entirely after the Festival arc and the actively working with Gajeel that was included.
So he was relatively easily forgiven, but not before he'd shown himself to be apologetic(in his own awkward way) and they were more or less even.
Gajeel helping Levy now is probably a combination of feeling though he still needs to make amends to her, him being impressed and intrigued by her during the Festival, and him wanting to get in on the S-Class trial action.