Biologically, they can't be salty when fresh. The tree would die if its internal juices were salty.
As Elendil said, fresh olives are practically inedible, or at least have a very unpleasant taste. This is why you can only get pickled olives, never fresh ones.
But olives differ by salt level. The worst offenders are probably Turkish stafidaki style olives (for some reason, they are saltier than Greek stafidaki style). They are small shrivelled black olives sold dry (without a brine). On the other end of the scale, you get some black Mamuts which are pretty bland. Markets with multiple olive types will sometimes note unusually high or low salt content on the label.
I find that many olives are not too salty to be eaten by themselves. They are salty, sure, but not more so than some dried meats. You may have gotten one of the saltier styles. You can try another style next time.
When you buy olives without knowing how salty they are, and they turn out too salty, you can remove the brine and keep them in clear tap water for 2-3 days, then eat.