The Lions dropped their grievance after reaching an agreement with the Bucs.
The Bucs previously had signed the restricted free agent to an offer sheet of three years' worth up to $9 million. But the Lions disputed the structure of the offer sheet, and the NFL assigned an independent arbitrator to look into the matter.
But that now becomes a moot point.
Johnson, 27, began his career in Tampa Bay until he was released in 2012. He spent the rest of 2012 and '13 with Minnesota before signing with Detroit last year.
He thanked the Lions on Wednesday for giving him a chance last season.
Detroit will always hold a special place in my heart, you guys gave me a chance when no one was willing; for that I'm grateful.— George Johnson (@GeoJohns92) April 15, 2015
In losing Johnson, the Lions' depth at defensive end takes a small hit. He had his most productive NFL season by far with Detroit in 2014, accumulating six sacks as a rotational defensive end behind starters Ezekiel Ansah and Jason Jones.
Ansah and Jones remain on what is now a reworked Detroit defensive line.
The Lions likely will replace Johnson with a combination of Devin Taylor, Larry Webster and potentially Phillip Hunt, who was signed earlier this offseason. Taylor played a rotational role as a rookie in 2013, but saw his snaps cut last season with the emergence of Johnson. Webster was drafted in the fourth round in 2014 as a developmental prospect who did not crack the defensive line rotation last season.
This is the third major loss in the offseason for the Detroit defensive line after losing tackles Ndamukong Suh and Nick Fairley in free agency. The team signed Tyrunn Walker and traded for Ngata to replace Suh and Fairley.
ESPN Lions reporter Michael Rothstein contributed to this report.