A few MorphOS users that bought a Sam460 had the price of OS4 refunded but I think that's something under EU law. There's probably no such law in the US but the new dealer there may prefer a sale without a few hundred dollars of bundled software than no sale at all. There's no harm in you asking now, at least you'll know if your concerns a valid or not.
@Kenny
Do you seriously believe that the bigger part of the X5000's market will be MorphOS users? Save the snarky comment about how few OS4 users you'd like to think there are. How do you think they are going to stop OS4 from running on the X5000 anyway?