When Free Software Depends on Nonfree

When a program is free software (free as in freedom), that means it gives users the four freedoms, so that they control what the program does. In most cases, that is sufficient for the program's distribution to be ethical; but not always. There are additional problems that can arise in specific circumstances. This article describes a subtle problem, where upgrading the free program requires using a nonfree program.

If the free program's use depends unavoidably on another program which is nonfree, we say that the free program is “trapped.” Its code is free software, and you may be able to copy pieces of its code into other free programs with good, ethical results. But you shouldn't