On Software: Open Source Licenses

Posted 2025-06-22 · Updated 2025-08-03

I mostly prefer permissive open source licenses that allow a lot but don’t restrict (or demand) much.
But this may also change, depending on specific projects and/or use cases…

Licenses often used by me

MIT License (MIT)

Very permissive, but has an attribution¹ clause that is phrased a bit vaguely:

… shall be included in all copies or substantial portions of the Software.

What counts as a copy of “the Software”? Only the source code? Or the machine-executable/binary artifacts too?
What is a “substantial portion”?

The BSL-1.0 is more specific in that regard.

Zlib/libpng License (Zlib)

Also a permissive license; attribution is prefered, but not required.
Altered versions must be marked as such and the license notes must be provided with any source distribution.

MIT No Attribution License (MIT-0)

Like the original MIT license, but without an attribution requirement; meaning that one does not have to name/deliver/display the copyright notice or the license terms of the original material.
Basically public domain².

BSD Zero Clause License (0BSD)

Similar to MIT-0: No attribution requirement; basically public domain².
Originally approved under the name “Free Public License 1.0.0”.
Despite its name, it’s actually just an alteration of the ISC license, and textually not derived from licenses in the BSD family (Wikipedia).

Boost Software License (BSL-1.0)

Similarly permissive as the MIT license, but without attribution requirements for binary distributions.
Compromise between MIT and MIT-0 or 0BSD.

Licenses often used by me

Further reading