The European Court of Justice made the decision in relation to a case that SAS Institute, a maker of statistical programs, brought against World Programming Ltd. (WPL), which develops and sells an interpreter for the SAS language.
Although WPL used and studied SAS's programs to understand their functionality, the court said, there was "nothing to suggest that WPL had access to or copied [SAS] source code." The court ruled that "the purchaser of a license for a program is entitled, as a rule, to observe, study or test its functioning so as to determine the ideas and principles which underlie that program."
If a function of a computer program could be specifically protected, that would amount to making it possible to monopolize ideas -- to the detriment of technological progress, the court said. This echoed the opinion given in November by Yves Bot, the court's advocate general.
The ruling effectively leaves the door open for companies to reverse-engineer the software of others -- in many cases without fear of infringing on copyrights.