Answer:
"software under copyright must not be in the public domain"
Explanation:
The conclusion of his argument is "software under copyright must not be in the public domain". This combines the two premises that were stated before it in order to form a logical outcome based on the premises. In the case of logic, this would basically be an
IF A and IF B, Then C
type of logic, in which A is "Public Domain Work can be copied", B is "Software under Copyright cannot be copied", and C is the conclusion which would be "software under copyright must not be in the public domain"