Hmm, I haven't thought of oiling my cutting board, and it doesn't look to me like it needs it. Sometimes when some of my other wooden kitchen implements look dried out I'll rub in a bit of whatever oil is at hand. Like, veg oil, olive oil, or ghee. If you're using it frequently I don't think the oil will have a chance to go rancid.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
I use walnut oil. It polymerizes on the wood and also does not go rancid. It is really the best of the healthy oils to use on wood (unless you are allergic to walnuts). It also has a pleasant smell. Coconut oil is my second pick. It can eventually go rancid but if you use your cutting board regularly you'll need to oil it again before the coconut goes rancid.
You can make a really nice treatment for your board by mixing the oil with melted beeswax (like you are making a comfrey salve or lip balm). The beeswax helps to give a better oiling to the wood.