Kenny, how is it treated. Do you just periodically oil it?

I use this product: Real Milk Paint Soapstone Sealer And Wood Wax
http://www.realmilkpaint.com/soapstone-sealer-wax.html

For the island did you glue the boards together? Would love to do something like this but my contractor said he is afraid it might buckle over time.

For this top we actually just used glue, no biscuits or dominoes. After 6 years, some checks in the wood have opened up a bit more, but the glue joints haven't moved. No buckling has occurred as it is anchored to the cabinet below, but it is also not a completely flat top, that's near impossible to achieve.

This is one of my favourite Houzz kitchens, and I hadn't realised that you've used old floor joists for the countertop! We've just salvaged pine floorboards in our 200yo house that are a good 2" x 10" x 12' or so, and I'm thinking I could copy your idea: what did you do to clean your boards up? Scrub with soap and water? Sand-blast? Did you re-plane them, or scrub them? t&g them?

We ran them through a planer and then glued them. If you plane too much you lose the character, but it would be hard to make a good counter without planing them somewhat to get flat surfaces to join