Where I can download older versions of foldx?

I have some scripts that call foldx 3b3. Is it possible to download an older version of foldx?

No, it is not possible. Foldx4 is supposed to be the same engine with an improved comand line/config file interface that is easier to use than FoldX3. Adapting the scripts is quite easy, but for any guidance just contact support at javier.delgado@crg.eu