Fun! We sealed our old oak floors with Rubio Monocoat. Smells lovely, environmentally friendly (beeswax and linseed oil), looked gorgeous, and very hard-wearing. This was in a kitchen, so it took quite a beating. You can also spot-repair it, which you can't do with standard urethane finishes.

You should be able to do just about any finish on this floor. You will (of course) properly sand (as per any hardwood floor) prior to product application. Rubio monocoat is coming up as very nice product that allows homeowners the ability to "self maintain" the finish for long periods of time (very, very low VOC content).

Water based polyurethane/urethane allows a clear coat finish = NO YELLOWING and LOW VOC. Oil modified polyurethane/urethane has higher VOCs with "light" ambering (turns a little yellow). Easy of application (for the professional) is part of the package.

Oil based products (aka "solvent" based) are the traditional products = strong ambering (dark orange over time) and high VOC content (only professionals should play with these). Can cause problems with chemical sensitive people (can take several weeks for the smell to go away). Many professionals "like" these because they "know" the products (they don't have to learn anything to use the product).

Choice is yours. Decide on your "chemical" (high VOC, moderate VOC, low VOC or very very low VOC) and find something appropriate from there.

Don't know anything about refinishing floors, but those are gorgeous!