Are the original cast going to be providing their characters' voices?

What I would say at this point is that we would love to have everyone. That is our first choice and we would hope to make that happen. Everyone has expressed interest. It's going to come down to the two biggest things in these cases, which are time and money, so we can't say yet.

Joss hopes to be able to make an announcement within the next two or three weeks in order to tell everyone what hopefully will be good news. In any event, people should rest assured that whoever is cast in the roles will be cast by Joss, and the idea is to make the characters sound and act like they do on the show.

It's not as though animated Willow is going to be written different from live action Willow. if she's not going to be Alyson, she is going to sound as much like Alyson as we can find.