He kept the earned bitcoin, but there are still very valid research purposes.
He could have easily have been trying to test gambling sites, tumbling sites, and number of the illicit sites with the earned coins.
Don't you see everyone? Just because he did something without permission doesn't mean he's not researching! He probably used those coins to research delivery speed from a number of BTC websites, or did the research to see how long it would take for inflation to render the money made from the coins minuscule!
Silly government!
There have been a number of people who have purchased bitcoin for legitimate research purposes such as being able to track/trace bitcoin throughout the network. bitcoin mixers have been tested by researchers. People have attempted to measure the number of TX that are actual trades as opposed to transferring one's own coins to another address they control.
You talked about illicit sites and so, and so I was playing along with the theme. I have read some of the stories talking about people using BTC to track it through the blockchain, and they are very interesting stories. But I don't believe that was the main topic in your statement.
Although, I didn't know about people using that to measure the amount of transactions. Thank you for bringing this to my attention!