Exim license
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| Exim license | |
|---|---|
| Name | Exim license |
| Author | Philip Hazel |
| Released | 1995 |
| Repository | Exim (MTA) |
| Os | Unix-like |
| Language | English |
Exim license The Exim license is a permissive free software license associated with the Exim (MTA) mail transfer agent, created by Philip Hazel. It has been referenced in discussions involving Free Software Foundation, Open Source Initiative, Debian Project, Red Hat, and Mozilla Foundation communities. Its text and interpretation have influenced licensing debates involving projects such as Sendmail, Postfix, qmail, NetBSD, and FreeBSD.
History and origin
The license originated during development of Exim (MTA) at the University of Cambridge under Philip Hazel, contemporaneous with licensing decisions by Sun Microsystems, BSD, Inc., and contributors to 4.4BSD. It was drafted at a time when projects like Apache HTTP Server and Linux kernel were crystallizing licensing practices and when organizations including the Free Software Foundation and Open Source Initiative were formalizing license categories. Historical interactions involved maintainers from Debian Project, Ubuntu, Gentoo, and repositories managed by GitHub and SourceForge.
Terms and conditions
The Exim license grants broad permission to copy, modify, and distribute the software, akin to terms found in the MIT License, BSD licenses, and the ISC license. It contains attribution and disclaimer clauses, addressing liability and warranty in a manner comparable to permissions used by OpenSSL and tools maintained by Netcraft. Specific clauses differ from the GNU General Public License family, and its language has been evaluated by legal teams at entities such as Canonical (company), Red Hat, Oracle Corporation, and academic counsel at Harvard University and Stanford University.
Compatibility and comparisons
Evaluations compare the Exim license to permissive frameworks like the MIT License, the 2-clause and 3-clause BSD licenses, and the ISC license. Compatibility assessments have been made by projects including Debian Project, FreeBSD, Gentoo, and organizations such as the Software Freedom Law Center and Open Source Initiative. The license’s permissive character contrasts with copyleft terms of the GNU General Public License and raises questions similar to those debated in cases involving OpenSSL and libpng.
Adoption and usage
Adoption is centered on Exim (MTA) deployments across distributions like Debian, Ubuntu, Red Hat Enterprise Linux, CentOS, Fedora, OpenBSD, FreeBSD, and NetBSD. Administrators at institutions such as CERN, NASA, MIT, Stanford University, and European Space Agency have encountered the license in mail infrastructure. Packaging teams at Debian Project and Gentoo have documented compatibility notes, while hosting providers such as Amazon Web Services, Google Cloud Platform, and Microsoft Azure include systems where Exim under this license is deployed.
Legal and practical implications
Legally, the Exim license’s warranty disclaimer and attribution requirements have been reviewed by counsel at Free Software Foundation, the Software Freedom Conservancy, and law firms with clients like Mozilla Foundation and Canonical (company). Practical implications concern integration with code under Apache License 2.0, MPL 2.0, and GPL families, prompting contributions policies at projects including Debian Project, Linux Foundation, and Apache Software Foundation. System integrators at Red Hat and SUSE consider the license when packaging for distributions and for compliance audits performed by organizations such as Black Duck Software and Snyk.
Controversies and notable disputes
Disputes have arisen in the broader ecosystem over license wording clarity similar to controversies involving OpenSSL and the GFDL. Discussions appeared on mailing lists of Debian Project, in issue trackers on GitHub, and in forums involving maintainers from Postfix, Sendmail, and qmail. Legal scholars at University of Cambridge and Harvard Law School have analyzed permissive licenses’ implications, and watchdog groups like Electronic Frontier Foundation have commented on compatibility and redistribution matters.