Microsoft's software is distributed under licenses that keep users divided and helpless. The users are divided because they are forbidden to share copies with anyone else. The users are helpless because they don't have the source code that programmers can read and change.
If you're a programmer and you want to change the software, for yourself or for someone else, you can't.
If you're a business and you want to pay a programmer to make the software suit your needs better, you can't. If you copy it to share with your friend, which is simple good-neighbourliness, they call you a "pirate".