In one of the DVD commentaries, Russell T Davies said that he intended for Jack to be Boe. He admitted that he left it open to interpretation, but the intention in his mind is that they are the same. RTD did that on several occasions, such as the woman in "The End of Time", whom he has stated that he intended to be the Doctor's mother, but since that's not stated onscreen it's left to the viewer.

I think that means I stumped someone but to each their own. I'll just have to think of a harder question. *wishes vehemently that someone would do this with Harry Potter because she could stump JK ROwling on a good day*