The agreements you describe are enforceable at law: if you violate them, your then-former-employer could sue you for monetary compensation for your use of the material and/or for a court order barring you from using it. You have to review the agreements you signed--while such agreements are, as stated, enforceable, they don't go further than their actual terms. If under their terms, you can sue this script, you can; but if their terms prohibit you from using it, you will be inviting legal action.