The anonymous online survey of more than 3,000 developers found that almost 70 percent of respondents keep a personal library of code that they freely carry from employer to employer. Such code is generally used without the lawful owner's knowledge or permission, according to Out-law.com, a site that provides legal advice on information technology and e-commerce.
"Reusing or copying code, though in some ways unlawful, I believe is common practice in software development," said one freelance developer who participated. "Most developers that I come in contact with (including myself) reuse, copy or even reverse-engineer code to make it work better or to include it in an application that we are programming."
According to Susan McKiernan, an IT lawyer with Masons, the law firm behind Out-law.com, the survey showed that there was a widespread acceptance of the practice of reusing and "borrowing" code.
McKiernan said the fundamental issue involved was whether a substantial part of the code had been copied.
"The problem lies in figuring out what is a substantial part of a software program," McKiernan said.
The courts say that you cannot define substantiality in terms of percentages of code, McKiernan said.
"You need to consider the skill and labor in design and coding which went into the specific bits of allegedly copied code," she said.
McKiernan points to one case in which a party copied only 2 percent or 3 percent of the total code, yet was found to have infringed copyright. In another successful infringement action, the developer had made considerable modifications and additions to the original software--making it visually very different and more user-friendly--but had nonetheless used the original software to take shortcuts.
The survey also revealed that developers do not realize that software does not need to be identical for copyright infringement to arise. Almost 90 percent said they would reproduce the way another piece of software functions, without copying any code.
"By consulting the original code and program, however, a developer could still be found to have copied a substantial part," said McKiernan.
Software companies also face a threat because the development work force tends to change jobs frequently, which increases the chances of employees and contractors introducing materials from previous employers, clients or elsewhere.
"The Internet adds a further risk, with the availability of software from anywhere in the world and the potential for code-sharing through forums and bulletin boards," said McKiernan.
And so does the pride that developers take in their software. Writing code is hard, and developers like to show off their work.
"I haven't met a developer who wants to hide his or her code," said one developer. "Developers are proud of their code and want other developers to see its brilliance (and feel proud if others use it). It's companies and managers who care about copyrighting code."
Michael Parsons of ZDNet UK reported from London.