We say allegedly because it's quite possible Delonte West's Twitter account could've been hacked. However, the grammar in the tweets and the fact that they haven't been deleted yet suggest it was West who let them fly.
Below is a screenshot of the tweets in question:
He and LeBron James have tumultuous relationship if you let people who believe the rumors tell it. While digging around trying to figure out whether or not @dluckleftwest is indeed Delonte's Twitter handle, we stumbled across this Cavsnation.com blog post with some interesting tidbits in it. The writer suggests the tweets were sent from a parody account and points to an interview Delonte did with Cleveland.com back in June of this year in which West had this to say about James:
If @dluckyleftwest isn't Delonte West, then why would his former D-League team and Jamario Moon tweet at him?
Mind you, Delonte West was diagnosed as bipolar in 2009, around the time he got brought up on weapons charges in September of that year. Also, a lot can happen between friends in six months, so Delonte singing LeBron's praises in June and not rocking with him anymore in December isn't that unbelievable.