They are entropic they require constant inputs of resources from the outside. Systems can be self-supporting, though perhaps over politically and culturally inconvenient timetables. They are synergetic they are more than the sum of their parts. A forest program requires that someone spend money on something from which they don't get a return it requires involuntary sacrifice by someone. A forest protecting system requires no sacrifice only tradeoffs.
Programs are reactive they happen after the fact.
Systems are preventive. Programs are usually divisible. Systems are not. A program divided in half is about half as useful as it otherwise would have been. A system divided in half is fundamentally different, and far less useful than as a distinct whole.