Abstract
19 years after its debut, Free Software has grown from an evangelist's movement into a critical part of software development. Firms and companies are eager adapters of free software, which boast modest price and robust stablity. However, free software are free as in freedom, not price. The majority of free software are licensed under Gnu General Public License, which implements a reciprocal clause, and requires certain obligations from licensees once they meet its criteria. Negligence of obligations may result in copyright infringement. In most cases, licensees can easily determine whether the criteria are met. Nevertheless, there are quite a few difficult boarderline cases, mostly involving interoperation of softwares. By studying the reciprocal clause, FAQs and other official statements from the Free Software Foundation, and underlying technology, this paper has developed a flowchart for determining whether obligations are due. Finally, this paper carefully selects a boarderline case that involves interoperation with GPL'd software, and analyize it with the flowchart.