Wirelessly posted (htc Pocket PC: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 8.12; MSIEMobile6.0) Sprint T7380)
It just means that if you continue go over the roaming data limit(whatever that is) they may charge you extra fees or they may threaten you with contract termination. When they say roaming is included they mean calls not data.
You can still tether but if you are tethering while roaming then you'll have to watch your KBs. Call them and ask what the limit is.