First off: no, I've never played The Mana World. It may be something I'm interested in, in the future, but I simply don't have the time now (so sorry =[).
So with that in mind, I'm also unsure how this exactly works. I read on the main page/FAQ that the game is open source, but I'm not sure how that extends to sprite images and using them outside of this game.
Which brings me to Fother.
Fother, guy, if you're reading this, amazing work on your sprites. I would have contacted you directly but I couldn't find a way to do so.
I'm doing a little game project and I needed to make a squirrel sprite. Googling different terms to try and get reference images and inspiration, I came across this sprite dump:

Although I realize this is a "monster", it is exactly what I need for a playable squirrel for a short little game I'm building. (In case you're curious, I'd be happy to tell you about it.)
I would like to request your permission to use this sprite dump as a resource, and if possible, commission you to do more, similar works if you'd be interested. Or even if you just want to be compensated for the use of these sprites it's something I'd consider. They're just amazing and practically exactly what I'm needing.
Thank you for taking the time to read this. Even if the answer is "you don't play my game so screw you" (which I doubt you'd be that mean) or any other form of "no", I'll respect it.
Chances are, as I only found this website through a fluke, I may not be able to find my way back here again. I'll try and check back, but no promises. If you (or someone else knowing how to contact Fother) would like to reach me, my personal email is Justin_Castillo@YMail.com. I would greatly appreciate any reply on the subject.
Thanks much.
Justin Castillo