1. It is not the developer's responsibility that you based your business on his product. Not to be a dick, but that is your fault. Much like the auto industry bailouts, that wasn't such a big deal because those companies are large... It was a big deal because there are 100 businesses within a 10 mile radius of this location and yours that rely on Ford, Chevy, Chrysler, etc for their business.
It is not the same for Twitter and TweetAttacks. They are absolutely not forms of income that you should base your life off of. And if you do.. Well, GLWT.
2. You are not entitled to anything. If the developer had 1/2 a brain, which I assume they do; the license would be for either the lifetime of the software or the lifetime of Twitter. How can they guarantee that..
A.) Twitter will be around when you are 90 years old.
B.) The developer will not die before you do.
C.) That something like this would not happen.
That's absurd and so is your basis for their source code. They've likely got tens of thousands of man hours in that software and just because you bought a lifetime license does not give you the right to molest their code with your cheap outsourced programming nonsense. People who work on stuff like that treat their CODE like a jewel. Because it is. And if for some reason this whole thing blows over or gets tossed out.... Imagine their remorse for GIVING AWAY their CODE for FREE.
3. They're being sued for SELLING a tool that encourages abusing Twitter's TOS. So there's probably tens of thousands of clients.
Imagine how much the amount they're being sued for would multiply if they GAVE the tool away FREE. That would be the second stupidest thing they could possibly do besides giving you their source code.
Bottom line, you are not entitled to jack nothing. If you bought the license yesterday, that's just TDB. You should not be basing your income, let alone your BUSINESS off any one tool. If you do, then it is nobody's fault but your own that you're in this situation.
.... Everything that ever happens to you in your life can always be traced back to something that YOU could have done differently. Blaming them for things happening to you is just a front so that you don't have to face the fact that it's your own fault.