Z:gnu-www-ja-free-sw--8e5b6a-One important way to modify a/en

One important way to modify a program is by merging in available free subroutines and modules. If the program's license says that you cannot merge in a suitably licensed existing module &mdash; for instance, if it requires you to be the copyright holder of any code you add &mdash; then the license is too restrictive to qualify as free.