looks like maple to me too! and i would be going crazy wanting to get it cut up asap!
however you might want to proceed carefully.
i would open up that log with the chainmill, and see what is inside, if it is as good as i suspect, it really ought to be cut up with a bandmill to get the best figure and highest percentage of useable wood out of the log.
furniture guys, turners, instrument builders go nuts over spalted maple, most especially if it has as i suspect some curly aspect too.
me? i would try my best to get as much quarter and rift sawn lumber from that spalted log, with a minimum thickness of 5/4s.
alternatively i would cut a few planks out of it to check the board quality, and then cut it into large blanks to be recut later, to order.
i would dearly love to have that log!
we get spalting here in standing live tree's, however it is usually found down in a hollowed out trunk and generally not very sound wood... hard to get em till the tree either falls over in a storm or a major branch break off... both of which seem not to happen as often with solid trunk tree's.
best of luck
bob g