Hmm, not the best Yew I've seen.
Don't risk trying to split 'em.
I'd say there is probably only 2 bows in the whole lot being pessimistic (dunno what you are supposed to do with a 4' length? Maybe one of your V short native American style bows? Or it may do billets like you said, but there's not a lot ow thickness to play with). The fattest one may saw and give two staves, but I doubt it.
My advice is to choose the cleanest straightest face of each piece, and chop/bandsaw away the oppsite side, to try and get one really good stave from each piece, much better than two bad ones.
I've made nice bows from small diameter stuff, so it's not a problem as long as you don't get greedy and try to squeeze out more bows than is sensible.
Even if you can only get 2 decent staves, for $15 you've done ok.
If it's been sitting for a year, chope 'em into staves get the bark off and slowly start working them down, the bark will have slowed the seasoning, but I'd think that if you work 'em down to roughed out bow size they'll be seasoned in a month maybe or two tops.
(You'll get a feel for how well seasoned they are when you de-bark 'em.)
Del