I was visiting a neighbor and the dog barks a lot. The owner passed it off as "he just barks". Once inside the house and sitting down, the dog came up and licked my face and I pet him. The dog walked away, came back and growled at me until the owner took him outside.

What does this mean?

Perhaps you were avoiding eye contact at first but once you relaxed you eyeballed him which is a threat in doggy rules ..it's hard to say ..

Without seeing the situation, it is impossible to tell why. It likely had to do with your response in body language.