User blog comment:BlankyXP/Nothing is true; everything is permitted./@comment-3184885-20121110144842/@comment-1344907-20121110145246

I've heard of that program, but you have to pay for it, right? :o

As for the lines being shaky, I dunno if there's a SAI equivalent, but there's a tool in GIMP called the line tool that may help you make the lines look a little neater.