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The intent of copyleft is to ensure freedoms for the recipients of derivatives of your works. In software that means the users of forks. Copyleft restricts you to the same license (or a compatible one) to prevent you adding more restrictions. ““More permissive”” software licenses can be redistributed with the same license but often it’s a more restrictive license (e.g. MIT -> proprietary).

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sugar_in_your_tea@sh.itjust.works ⁨2⁩ ⁨weeks⁩ ago
You can’t remove the license, say MIT, or add any restrictions to the code. You can combine it with other works and distribute the combined work under different terms, provided you still abide by the terms of the license (e.g. source distributions need to retain the license, binary distributions don’t).

Copyleft forces modified distributions to have the same terms as the copylefted software. If you have some MIT code and some GPL code and you combine it, the combined work is GPL. Likewise if you combine proprietary code and GPL, the combined work is GPL, and that’d regardless of how it’s distributed.

Permissive licenses protect the source as it was when it was combined into the other work. Copyleft licenses enforce distributed changes to the source are made available under the same license. Which one you want depends on what “freedoms” you want. Do you want the freedom to use the source however you want, including with proprietary code? Then you want a permissive license. Do you want to ensure that any changes to the code are always available? Then you want copyleft code.

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- tabular@lemmy.world ⁨2⁩ ⁨weeks⁩ ago
  With the minimal amount of work added the combined work can now have added restrictions. They’re pushover licenses.
  
  Devs are free to choose whatever license they want but in the pathfinding problem of interacting with others then “protecting the source” is the wrong target node. Copyleft is a tool to help people.
  
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  - sugar_in_your_tea@sh.itjust.works ⁨2⁩ ⁨weeks⁩ ago
    Your first paragraph is a bit misleading.
    
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    Let’s use an example of the MIT license, perhaps the most permissive (license text below). This license only applies to the source code, so it allows you to distribute executables under any terms you like. So the combined work here is not under the terms of the MIT license, but whatever terms the distributor wants. If the combined work is distributed in source form, then any modifications you make are under the MIT license unless you make it explicit which parts are licensed differently. If users don’t like the license terms for your changes, they can remove them and be subject to only the terms of the code they keep. You cannot change the terms of existing code. Since the MIT license doesn’t obligate users to release their modifications or combined work, it’s more attractive to businesses, and businesses frequently upstream their changes to reduce their own maintenance burden. A lot of changes are not upstreamed though.
    
    MIT license text
    Copyright © 2025 <copyright holders> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    
    Choice of license depends strongly on how you want others to use it. If you want it to appeal to businesses as a library (and attract fixes from their full-time devs), a permissive license is a good bet. If you want it to be a community developed thing or perhaps an application, copyleft can make a lot of sense. I’ve like all FOSS licenses and I’ve released projects under everything from the MIT license to the AGPL.
    
    My preferred license barring any other considerations is the MPL (copyleft at the file level), but there are usually other considerations.
    
    My only ask is that people use a standard license instead of DIYing one (or not using one). You can also change your license at any time, provided you’re the only contributor or every other contributor agrees (otherwise you’d need to selectively remove their contributions).
    
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