If a cause came from outside of this universe, then it came from outside the realm of cause-effect relationships. So, the cause can be said to be uncaused. Because it is outside this realm, it doesn't necessarily need a cause itself. To say otherwise would be to impose the rules of this system onto something outside of it. This would apply to all hypothetical causes from outside this universe. Therefore, an uncaused cause does not necessarily have to be God.
William Lane Craig has said that this hypothetical uncaused-cause would have to be timeless, changeless, immaterial, eternal, and personal.
It seems to me, however, that one could not necessarily ascribe to this uncaused-cause ANY characteristics found within this universe because the cause is from without the universe. All of the characteristics we know are of things within the universe. So, I don't think Craig is justified in calling it "personal". To do so is to impose a characteristic found within this universe upon something without this universe.
Interesting to note is how this reasoning would also apply to describing other universes. I wonder how scientists have gotten around this problem in their theories of a multiverse.