It means that these people are not kept from learning how others succeeded. Bear in mind that many programmers work under restrictions that forbid them from seeing others' code. Rather than sit on the shoulders of those who went before, which is the best way to see ahead and to advance, they are thrown into the mud. The right to study is the right to look ahead, to advance, by sitting on the shoulders of giants. Moreover, the right to study means that the software itself must be made available in a manner that humans can read.
Software comes in two forms, one readable only by computers and the other readable by people.
The form that a computer can read is what the computer runs. This form is called a binary or executable. The form that a human can read is called source code. It is what a human programmer creates, and is translated by another computer program into the binary or executable form. The next right, the right to modify, is the right to fix a problem or enhance a program.