About Spriting

[Phaze]

As far as I know, the only features of GG that are shareware-version specific are the support for GIF, ICO, CUR and ANI files.
There's alternatives for all of these (I use the RealWorld cursor editor for CUR and ANI, @icon sushi for ICO (it has nice multi-image icon support)) if you should need to use them (chances are you won't, I do because I make windows cursors and programs sometimes).

GIMP also has support for ICO and of course, GIF
I doubt it supports ANI/CUR but it might. I haven't checked
I just wish they'd add APNG support natively, even if there is a plugin for it.