Free Software, Free Society: selected essays of Richard M. Stallman. 2nd edition.

This problem can occur in any kind of software, in any language. For instance, a free program that only runs on Microsoft Windows is clearly useless in the Free World. But software that runs on GNU/Linux can also be useless if it depends on other nonfree software. In the past, Motif (before we had LessTif) and Qt (before its developers made it free software) were major causes of this problem. Most 3D video cards work fully only with nonfree drivers, which also cause this problem. But the major source of this problem today is Java, because people who write free software often feel Java is sexy. Blinded by their attraction to the language, they overlook the issue of dependencies and fall into the Java Trap.

Sun’s implementation of Java is nonfree. The standard Java libraries are nonfree also. We do have free implementations of Java, such as the GNU Compiler for Java (GCJ) and GNU Classpath, but they don’t support all the features yet. We are still catching up.

If you develop a Java program on Sun’s Java platform, you are liable to use Sun-only features without even noticing. By the time you find this out, you may have been using them for months, and redoing the work could take more months. You might say, “It’s too much work to start over.” Then your program will have fallen into the Java Trap; it will be unusable in the Free World.

The reliable way to avoid the Java Trap is to have only a free implementation of Java on your system. Then if you use a Java feature or library that free software does not yet support, you will find out straightaway, and you can rewrite that code immediately.

Sun continues to develop additional “standard” Java libraries, and nearly all of them are nonfree; in many cases, even a library’s specification is a trade secret, and Sun’s latest license for these specifications prohibits release of anything less than a full implementation of the specification. (See http://jcp.org/aboutJava/communityprocess/JSPA2.pdf and http://jcp.org/aboutJava/communityprocess/final/jsr129/j2me_pb-1_0-fr-spec-license.html for examples.)

Fortunately, that specification license does permit releasing an implementation as free software; others who receive the library can be allowed to change it and are not required to adhere to the specification. But the requirement has the effect of prohibiting the use of a collaborative development model to produce the free implementation. Use of that model would entail publishing incomplete versions, something those who have read the spec are not allowed to do.

In the early days of the free software movement, it was impossible to avoid depending on nonfree programs. Before we had the GNU C compiler, every C program (free or not) depended on a nonfree C compiler. Before we had the GNU C library, every program depended on a nonfree C library. Before we had Linux, the first free kernel, every program depended on a nonfree kernel. Before we had BASH, every shell script had to be interpreted by a nonfree shell. It was inevitable that our first programs would initially be hampered by these dependencies, but we accepted this because our plan included rescuing them subsequently. Our overall goal, a self-hosting GNU operating system, included free replacements for all those dependencies; if we reached the goal, all our programs would be rescued. Thus it happened: with the GNU/Linux system, we can now run these programs on free platforms.

The situation is different today. We now have powerful free operating systems and many free programming tools. Whatever job you want to do, you can do it on a free platform; there is no need to accept a nonfree dependency even temporarily. The main reason people fall into the trap today is because they are not thinking about it. The easiest solution to the problem is to teach people to recognize it and not fall into it.

To keep your Java code safe from the Java Trap, install a free Java development environment and use it. More generally, whatever language you use, keep your eyes open, and check the free status of programs your code depends on. The easiest way to verify that a program is free is by looking for it in the Free Software Directory (http://fsf.org/directory). If a program is not in the directory, you can check its license(s) against the list of free software licenses (http://gnu.org/licenses/license-list.html).