Currently, there is not a way to change the program to "require registration" or vice versa after it has already been created. 

If no tickets have been sold to any events under the program:
  1. From under Tickets > Program search > Select the Program
  2. Delete the program and add it again
If tickets have already been purchased for program events:
  1. Refund all tickets sold to the program
  2. Mark the program as inactive (and change it to a name such as "DO NOT USE - INACTIVE PROGRAM")
  3. Add the program again and check the "Requires registration" box when creating it
  4. Re-enter the sales orders