unix was developed in 1969, tripos was based on unix and written in bcpl a c-like language in 1976, later when the os was being develped for amiga a change was made when metacomco was contacted for an os. they took a 68k version of tripos and developed it for the amigas hardware.
in the 80s many many programs were ported from unix for the amiga including rendering programs, text stuff, spreadsheet programs, lots of postscript programs etc etc. go to aminet and type in unix into the search you will find lots of programs including games that were ported
go to google or any other search engine and type in amigados unix tripos and you will find os history sites some of which actually call tripos a unix clone although it is not. amigados is a direct offshoot of tripos, which is an indirect ofshoot of unix. there was a lot of os development especially in american universities in the 70's that was based more or less on unix. including minux which infuenced linux.
software porting has stopped for many reasons not the least of which is the fact that many of the programmers who were doing the porting have moved over to linux, and the fact that most amigans dont run an x-window server which is neccisary for newer software even though they could.