From the VeloNews article, it's quite clear it's because of Greg's comments regarding Armstrong:
"Greg's public comments hurt the LeMond brand and the Trek brand," Burke said.
I'm not sure yet what to think about it... Maybe it has to do with Richard Burke's recent death. Greg had nice words about him:
Greg LeMond, who sold his bike brand to Trek in the early 1990s, called Burke a visionary.
"My heart goes out to the Burke family and the entire extended Trek family," LeMond told VeloNews.
"He was a visionary in the world of cycling and together with his son, John, built an incredible family business. I will always remember him as a man of integrity and he will be dearly missed."
Maybe his relationships with John Burke, son of Richard, is not so good.
As Greg said himself, it's no fun having a muzzle, and his deal with Trek has been a big one for long.
Let's wait and see what will come out of it...