What he means can be speculated on many levels. One he is also interested, two : he does not to appear rude, three: he may have not known what his schedule is and did not feel like giving a straight answer, four: he did not want to go and tell you that in order not to afflict your feelings.
It is best to ask the person directly for a straight answer. A man should not have too much of a difficulty saying what is on his mind. If you have asked him out more than once, it may be a good idea for you to wait for him to make a move. If he is interested he will.