Reverse engineering
Reverse engineering of the Skype protocol by inspecting/disassembling binaries is prohibited by the terms and conditions of Skype's license agreement. However European Union law allows reverse-engineering a computer program without getting a permission from an author for inter-operability purposes. In the United States, the Digital Millennium Copyright Act provides protections for reverse engineering software for the purposes of interoperability with other software. There are also legal precedents in the United States when the reverse-engineering is aimed at interoperability of file formats and protocols.