Pokenet uses slick2D which doesn't support animated Gif's (it'll load them, but only the first frame)
You'll have to find a way around this such as using AWT.
Another way you could do this would be to convert all the animations to sprite sheets (Which they currenty have on spriters resource) and have slick load them using the animation function.
Xerixe currently has this system implemented and -Default kept saying he planned on releasing his edits along with Xerixe, but after all the talk for months, they still haven't done so.
Anyway, good luck on it.