As of December 2006, Sun is in the middle of rereleasing its Java platform under the GNU GPL. When this license change is completed, we expect that Java will be no longer be a trap. Notwithstanding that, the general issue described here will remain important, because any non-free library or programming platform can cause a similar problem. We must learn a lesson from the history of Java, so we can avoid other traps in the future.
April 12, 2004
If your program is free software, it is basically ethical--but there is a trap you must be on guard for. Your program, though in itself free, may be restricted by non-free software that it depends on. Since the problem is most prominent today for Java programs, we call it the Java Trap.
A program is free software if its users have certain crucial freedoms. Roughly speaking, they are: the freedom to run the program, the freedom to study and change the source, the freedom to redistribute the source and binaries, and the freedom to publish improved versions. (See http://www.gnu.org/philosophy/free-sw.html.) Whether any given program is free software depends solely on the meaning of its license.
Whether the program can be used in the Free World, used by people who mean to live in freedom, is a more complex question. This is not determined by the program's own license, because no program works in isolation. Every program depends on other programs. For instance, a program needs to be compiled or interpreted, so it depends on a compiler or interpreter. If compiled into byte code, it depends on a byte code interpreter. Moreover, it needs libraries in order to run, and it may also invoke other separate programs that run in other processes. All of these programs are dependencies. Dependencies may be necessary for the program to run at all, or they may be necessary only for certain features. Either way, all or part of the program cannot operate without the dependencies.
If some of a program's dependencies are non-free, this means that all or part of the program is unable to run in an entirely free system--it is unusable in the Free World. Sure, we could redistribute the program and have copies on our machines, but that's not much good if it won't run. That program is free software, but it is effectively shackled by its non-free dependencies.
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 non-free 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 non-free 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 they fall into the Java Trap.
Sun's implementation of Java is non-free. Blackdown is also non-free; it is an adaptation of Sun's proprietary code. The standard Java libraries are non-free 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 non-free; 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, which 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 non-free programs. Before we had the GNU C compiler, every C program (free or not) depended on a non-free C compiler. Before we had the GNU C library, every program depended on a non-free C library. Before we had Linux, the first free kernel, every program depended on a non-free kernel. Before we had Bash, every shell script had to be interpreted by a non-free 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 non-free 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 of the Java Trap is to teach people not to 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://www.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://www.gnu.org/licenses/license-list.html).
We are trying to rescue the trapped Java programs, so if you like the Java language, we invite you to help in developing GNU Classpath. Trying your programs with the the GCJ Compiler and GNU Classpath, and reporting any problems you encounter in classes already implemented, is also useful. However, finishing GNU Classpath will take time; if more non-free libraries continue to be added, we may never have all the latest ones. So please don't put your free software in shackles. When you write an application program today, write it to run on free facilities from the start.