Open source software, comprising up to 90% of the modern software stack, faces ongoing challenges between open and proprietary models. The two main types of licenses are 'permissive,' allowing for minimal restrictions, and 'copyleft,' which mandates that modifications remain open source. Popular licenses include MIT, which lacks explicit patent rights, and Apache 2.0, which offers patent protection. The GNU GPL and AGPL licenses ensure community contributions remain open. The rise of cloud computing has also spurred interest in the AGPL license, while other licensing models like dual licensing and 'faux-pen' source are emerging.