The trio departed the club at the end of their contracts at St Mary's, while Cody Cropper, Lloyd Isgrove, Sam McQueen, Omar Rowe and Jake Sinclair have all been offered extended stays.
Guly is the biggest departure, having made 118 appearances and scored 23 goals during four seasons with Saints
The Brazilian helped the club rise from League One to the top-half in the Barclays Premier League, while Barnard and Forte played their own parts in the back-to-back promotions before spending time on loan in the Football League.
A number of younger players have also been informed that they will not be offered new contracts, including development squad members Matt Young, Joe Curtis and Andy Robinson.
Jamal Branker, Fraser Colmer, Charlie Higgins and James White are others to leave, while Tom Leggett and Isaac Nehemie have joined Aston Villa on professional terms after being told of their release by Saints.
Corby Moore has joined newly-formed North American Soccer League side Indy Eleven after being informed the same.
Source : PA
Source: PA