Alrighty, after some inquiries at Kerberos Productions (the people who made sots) they told me the following:
As long as you do not profit from your mod, and give credit to the original source and voice actors, there is nothing to stop you.
So now that's out of the way look for my mod end of this week/beginning of the next.
Most everyone who;s bothered to give input has mentioned Hivers (voice sample #3) so I'll be doing them first, and might do the Tarkas afterwards if anyone has a real desire to see their voices rather than the Hivers.