Jackson's contract calls for him to make $10 million next year but he has no guaranteed money remaining on his deal.
In addition to Jackson, the Eagles get a seventh-round draft pick in 2020, while a 2019 sixth-round pick heads to the Buccaneers, a source told Mortensen.
The 32-year-old Jackson was dumped by the Eagles after posting what still stand as career highs in receptions (82), yards (1,332) and TD catches (nine) in the 2013 season.
He has played the last two seasons in Tampa Bay. Jackson finished with 41 catches for 774 yards and four touchdowns in 12 games last season.
The Eagles feature three receivers - Jordan Matthews, Golden Tate and Mike Wallace - with expiring contracts who could be lost by the end of this week. Then-Eagles coach Chip Kelly cut Jackson in 2014, leaving him to sign with the rival Washington Redskins as a free agent.
Jackson, 29, wasn't expected to be on the market long as he still looks to be a top-5 three-technique pass rusher in the league in the interior.
Since the Jacksonville Jaguars released veteran defensive tackle, Malik Jackson, he was available to sign a new deal on Monday, despite Free Agency not beginning just yet.