My current license preference is the ISC license which was first written by the Internet Systems Consortium (ISC). I like it for the following reasons:
- It is brief.
- If is a permissive license (not a copyleft license).
- It is compatible with the Open Source Definition (OSD) as specified by Open Source Initiative (OSI).
- It is compatible with GNU's GPLv2 and GPLv3 (FSD) and is listed as GPL-Compatible Free Software License by the Free Software Foundation.
- It is about as free as you can get from constraints and hassles for both the user and the copyright holder.
- It is more certain than releasing a work to the "public domain" because "public domain" has no legal definition in many jurisdictions.
Copyright (c) [4-digit year(s)], [company or person's name] <[email address]> Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
The ISC license is functionally equivalent to the "two-term BSD license", "MIT license", "X11 license", and "X Consortium license", but the ISC license is shorter and more clear.
The ISC licence is OpenBSD's preferred licence for new code.
Releasing a work into the "public domain" may appear to be the least restrictive way to release a work, but this is not so because "public domain" has no legal definition in many jurisdictions. In other words, you, as a copyright holder, cannot release a work into the "public domain". This is counter-intuitive. A public domain release statement may be legally meaningless and have the same effect as releasing a work without a license. This creates a burden on the user because they may not really be sure they can redistribute or release software without restrictions that is based on your purportedly public domain work.
This is not just a license. It has three parts: the copyright claim; the license statement; and the responsibility disclaimer.