Typically employed developers get paid per time (i.e. hourly or monthly salary). Contractors may be either per hour or a fixed sum to deliver to an agreed-upon

Typically employed developers get paid per time (i.e. hourly or monthly salary). Contractors may be either per hour or a fixed sum to deliver to an agreed-upon specification. With scriptwriting (and often art in general) you first develop the "product" and then try to find a buyer. This is IMHO not a feasible model for individual software developers.