Without more details the whole story sounds iffy. Since he did not give us more details but still shared his story I will speculate that he took advantage of what he thought were some clever tax loopholes in MA. Remember that hid did state very passingly that he has a presence in MA. Specifically this:
>>Again, I hadn't lived there or worked there since 2003, but I did own part of a business that was headquartered in MA, and the state was using this fact to harass me for income tax money<<
So in essence, he probably took advantage of some iffy tax loop hole which the state now probably disagrees with and is asking for whatever it thinks it is owed.
As with all these stories, need to be taken with a nice handful of salt. Owning a business in MA would make it seem like you would qualify for state taxation (on that part at least).
The US taxes its citizens even outside of their own jurisdiction. It wouldn't surprise me if MA taxed people that still made money in MA.
All states (that have an income tax) do. I own property, which I rent, in multiple states including MA. I need to file tax returns for the income I make in each of them. Nothing unusual there.
>>Again, I hadn't lived there or worked there since 2003, but I did own part of a business that was headquartered in MA, and the state was using this fact to harass me for income tax money<<
So in essence, he probably took advantage of some iffy tax loop hole which the state now probably disagrees with and is asking for whatever it thinks it is owed.