 In June 1989 , " Networking Release 1 " or simply Net @-@ 1 – the first public version of BSD – was released . After releasing Net @-@ 1 , Keith Bostic , a developer of BSD , suggested replacing all AT & T code with freely @-@ redistributable code under the original BSD license . Work on replacing AT & T code began and , after 18 months , much of the AT & T code was replaced . However , six files containing AT & T code remained in the kernel . The BSD developers decided to release the " Networking Release 2 " without those six files . Net @-@ 2 was released in 1991 . 
