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Reverse Engineering Software: Is It Safe?

April 1990

One of the most controversial computer-related issues that has been debated as the European Economic Community struggles toward the 1992 Initiative is whether the act of decompiling or disassembling computer software should constitute a copyright violation. Some industry groups, including members representing Japanese interests, argue that decompilation should be permitted where necessary to achieve compatibility. They argue, for example, that decompilation may be necessary even to achieve data compatibility. This position is strongly opposed by many U.S. software companies, which take the position that decompilation should be considered a copyright infringement.

While this debate rages in Europe, there is considerable uncertainty over the legal consequences of decompilation of software under U.S. copyright law.

Most software programs are distributed in object code form to prevent the disclosure of trade secrets in the software. However, the increasing sophistication of computer programs which perform decompilation and disassembly often allows the conversion of object code into a human readable form that reveals the logic and engineering of a program.

When a program (often referred to as the “target program”) is decompiled, technically speaking a “copy” is made, and the creation of that copy may constitute copyright infringement. If the copier then markets a new program that contains the expression of the target program, the copier will be subject to prosecution for copyright infringement. The infringement is less clear if the copier is careful not to copy any of the expression of the target program, but only its ideas or algorithms, which are not protected by copyright law. Has infringement occurred if the copier performs the decompilation to determine formats and protocols for the purpose of creating compatible software, but does not copy protected expression from the target program?

In these instances, the owner of the original work’s only argument under the copyright law is that the work being distributed is illegal because it could not have been created but for the copy that was illegally generated during the process of decompilation. To put it another way, the owner must argue that although the program being distributed is not itself infringing, it is tainted by the fact that one of the steps in its creation was illegal.

Based on cases decided thus far, the U.S. courts seem unlikely to order a company to take its software program off the market because one of the steps leading to the creation of that software involved the improper creation of a copy. In several cases the courts disregarded the fact that a technical illegality occurred when programs were dumped from a ROM or EPROM, so long as the resulting program was not similar to the target program. However, is it not clear that the courts in these cases directly addressed the issue of whether dumping the code was itself a copyright infringement.

Underlying the “letter of the law” here is an important policy issue: should programs protected only by copyright law be subject to reverse engineering, so that society can benefit from dissemination of the unprotected ideas in the programs, or should copyright law permit copyright owners to do what copyright law never has done in the past, that is, allow them to use the copyright to prevent reverse engineering?

TLB Comment : The copyright issues associated with decompilation overlap with contract law. Where there is a negotiated and executed license agreement that prohibits decompilation, the restriction will be enforced as a matter of contract, not copyright. However, where the software is contractually protected only by a shrink-wrap license, there is serious doubt whether such a contract is enforceable, and therefore whether a contractual prohibition on decompilation has any legal effect.

Readers should not conclude, based on the analysis and discussion in this article, that decompilation of software not subject to an enforceable license agreement is free from risk of legal liability. Until the courts begin to address the issue directly, decompilation of copyrighted software may lead to a serious risk of prosecution for infringement.

Postscript: A later article discusses two cases dealing more definitively with this topic. Please click on the article name to see that article:

Reverse Engineering Software to Achieve Compatibility is Fair Use (January 1993)