A common misconception about free software is that having a free license is both a sufficient and necessary condition for the software to be free. There might be cases when software is too simple to be restricted by copyright, so it is not a necessary condition. There are much more important arguments why it is not sufficient.
Copyright is used to restrict sharing of a work. This is often used to prevent users from cooperating with other users, while this can be used to prohibit some restrictions of the freedom of derivative work users in a practice called copyleft. Although copyleft can limit freedom of users modifying software (works under different copyleft licenses usually cannot be merged in one derived work), this is practically a useful compromise which won’t be discussed in this essay.
The most obvious way to restrict user’s freedom is to not share with them a source form of the program. There are many sourceless blobs of microcode in the kernel called Linux, while they have free licenses ‘giving’ users freedom that they cannot use. Without copyright (or with a very short one), there would be no effect on restrictions of nonfree software, only copyleft would be limited. Digital restrictions management clearly shows that copyright isn’t important for software owners: they make and enforce their own rules restricting what the user can do (actions allowed by copyright laws are also restricted by DRM).
DRM wouldn’t be effective if the user could understand the program (difficult, although possible even without source code as some cases in cryptography show) and install a different one. The second part is prevented by nonmodifiable bootloaders that can load only software signed by the device manufacturer. This is a common practice for phone and tablet operating systems using much GPLv2-licensed software, named tivoization after an early case.
Although free software licenses can protect users from the above problems in derived works, there are different legal issues that won’t be avoided in this way. Software patents are one of them. Governments censoring useful cryptography or pornography are similarly a restriction of software user’s freedom (and non-user’s).
These examples show that free software licenses aren’t sufficient for software to be free, while they don’t suggest any obvious solutions to this problem. They clearly require user’s awareness of their (not necessarily software-related) freedom. The focus on licensing leads to them not considering these issues restrictions of their freedom. It could also limit the visibility of copyright problems making other alternatives (with appropriate replacements for copyleft) more beneficial in a longer term.