Open Source Software maintenance and reuse require identifying and comprehending the applied software licenses. This paper first characterizes software maintenance, and open source software (OSS) reuse which are particularly relevant in this context. The information needs of maintainers and reusers can be supported by reverse engineering tools at different information retrieval levels. The paper presents an automated license retrieval approach called ASLA. User needs, system architecture, tool features, and tool evaluation are presented. The implemented tool features support identifying source file dependencies and licenses in source files, and adding new license templates for identifying licenses. The tool is evaluated against another tool for license information extraction. ASLA requires the source code as available input but is otherwise not limited to OSS. It supports the same programming languages as GCC. License identification coverage is good and the tool is extendable.