This account last posted in 2013 and it does seem very strange that it is becoming active again now. It might be the original owner, but who knows - their is no such thing as a "legal heir" to a bitcointalk account so that is a weird reference to make. Somebody should probably tag the account until the identity is proven, because there is so much account password cracking going around.
I wish you read the news before posting, Hal was the person to receive world's first bitcoin transaction
directly from Satoshi. He passed away in 2014 and now we don't know who is using his account. He was next important person after Satoshi in bitcoin.