Probably stupid questions for you clever folk, but here goes:
Why do I need to withdraw coins from the Ultracoin pool before midnight tonight...what if I dont?
Very clever questions indeed!
As you
can read earlier, official Ultracoin goes to mandatory update with NF14 and block reward reducing.
This changes of the Ultracoin protocol are not backwards-compatible; i.e., older client versions would not accept blocks created by the updated client, considering them invalid. Obviously, this can create a blockchain fork when nodes running the new version create a separate blockchain incompatible with the older software.
If you withdraw coins before fork point (01 Nov 2015 00:00:00 GMT), you'll be able to use them in both blockchains.