Identifying licensing of jar archives using a code-search approach

Free and open source software strongly promotes the reuse of source code. Some open source Java compo- nents/libraries are distributed as jar archives only containing the bytecode and some additional information. For whoever wanting to integrate this jar in her own project, it is important to determine the license(s) of the code from which the jar archive was produced, as this affects the way that such component can be used. This paper proposes an automatic approach to determine the license of jar archives, combining the use of a code-search engine with the automatic classification of licenses contained in textual files enclosed in the jar. Results of an empirical study performed on 37 jars—from 17 different systems—indicate that this approach is able to successfully infer the jar licenses in over 95% of the cases, but that in many cases the license in textual files may differ from the one of the classes contained in the jar.