Proprietary licences give you the most control. You as the licence holder would simply refuse to grant a licence to any party involved in matters you do not condone. You could add an EULA that explicitly states this, and have legal staff at hand to follow up on any misuse. This is a costly option though.
Free software licences are not an option. Forbidding specific use of your software goes against the intent of the commonly accepted free software licences — you would run afoul of freedom 0:
The freedom to run the program as you wish, for any purpose¹
There probably exist other open source (but not free software) licences that do limit the audience, but you probably won't be able to enforce them, and they tend not to be taken seriously. You would on the other hand frustrate users outside of the military who want to legally use your software in ways normally permitted by free software licences — e.g., by reusing parts of it, forking it, combining it with other free software, etc.
Lastly, the absolute sure-fire way of preventing any military use of your software is not releasing it at all.
I don't think it's worth the hassle to add such a clause. If the point is not to actually prevent its use, but to make a statement, then make a statement on the project's homepage and in the documentation. It will have the same effect without resorting to weird software licences, and you can choose a well-known free software or merely open source licence.
Why can't he have his own license like Qt has? They have free version for individuals and paid version for commercial use.
The free version of Qt can also be used for commercial purposes - otherwise this would violate freedom 0. The paid version is for people who prefer different license terms instead of the imposed open source terms.
He could make a non-free (i.e., violating the four free software freedoms), non-OSI approved open source licence that does this, but it wouldn't be as permissive as you would probably want it to be, and it wouldn't be compatible with licences that are.
IANAL, but I guess license one would still not be free software, and might still be incompatible with, say, the GPLv3. So you might still prevent non-military individuals from using your code.
Comments
Proprietary licences give you the most control. You as the licence holder would simply refuse to grant a licence to any party involved in matters you do not condone. You could add an EULA that explicitly states this, and have legal staff at hand to follow up on any misuse. This is a costly option though.
Free software licences are not an option. Forbidding specific use of your software goes against the intent of the commonly accepted free software licences — you would run afoul of freedom 0:
There probably exist other open source (but not free software) licences that do limit the audience, but you probably won't be able to enforce them, and they tend not to be taken seriously. You would on the other hand frustrate users outside of the military who want to legally use your software in ways normally permitted by free software licences — e.g., by reusing parts of it, forking it, combining it with other free software, etc.
Lastly, the absolute sure-fire way of preventing any military use of your software is not releasing it at all.
I don't think it's worth the hassle to add such a clause. If the point is not to actually prevent its use, but to make a statement, then make a statement on the project's homepage and in the documentation. It will have the same effect without resorting to weird software licences, and you can choose a well-known free software or merely open source licence.
1: https://en.wikipedia.org/wiki/The_Free_Software_Definition
The open source license doesn't have to discriminate if the author has 2 licenses from the start.
1) License one grants all open source rights to individual use.
2) Government and state-level entities require a commercial license to use it.
Just don't mention the military.
When the government requests a license, ask what it is ifor. If it's for hospitals or charity, give the license.
If it's for one more war waged for bankers, then tell them the license is 2 billion dollars.
"all open source rights" implies freedom 0: "The freedom to run the program as you wish, for any purpose".
Does OP require the license to be OSI approved?
Why can't he have his own license like Qt has? They have free version for individuals and paid version for commercial use.
The free version of Qt can also be used for commercial purposes - otherwise this would violate freedom 0. The paid version is for people who prefer different license terms instead of the imposed open source terms.
He could make a non-free (i.e., violating the four free software freedoms), non-OSI approved open source licence that does this, but it wouldn't be as permissive as you would probably want it to be, and it wouldn't be compatible with licences that are.
IANAL, but I guess license one would still not be free software, and might still be incompatible with, say, the GPLv3. So you might still prevent non-military individuals from using your code.