Some random thoughts/questions:
If it's really soft....don't use it. Food will likely contaminate the soft spots (liquids/blood/etc. soaking into those areas) and make bad mojo. I've seen spalted maple I could dig at with my fingernails and would never use anything that soft for a cutting board. Maple is a great cutting board material partially because of it's closed grain structure which prevents alot of that penetration.
If it's still "green", don't do anything until it's been properly dried.....a year maybe?!?! Less if stored in really dry location or if it's not very thick...hard to tell in the pics.
Spalting is supposedly bad for you....although I don't know how much and if it really matters all that much. Some board makers refuse to use spalted woods for this reason alone.
Depending on how thick it is, how green it is, and how thick you plan to leave it....I would not really recommend using one piece as a cutting board. Cutting boards are made up of pieces for a reason...it's more stable. A really thick piece would work better...think of those Chinese tree trunk blocks.....but they still often times crack.
It looks like a beautiful board, and I'd love to see this get made into a big arse cutting board...so I would hate to see you make something and have it warp, crack, etc. beyond useage when a little extra work/thought now could make it into something your grandchildren could use.
