According to Darren Urban, he received a text from Al Johnson that the team has released him but there's no official word from the team yet. The move should save the team some considerable cap space and it bodes well for the idea that Lyle Sendlein is the long term starting center. AJ was on IR so this won't affect the 53 man roster.
Update: It's looking pretty official now with Kent Somers now confirming the reports and also reporting that Johnson is planning on filing a grievance against the team. He's contending that he isn't fully recovered from two off season knee surgeries and a team isn't supposed to cut an injured player. The two parties must not have been able to agree on an injury settlement. AJ was scheduled to make $3.5 million this year and the next two seasons.