If a paper under the CC BY-SA 4.0 describes &amp; designs a software X &amp; its implications, does said software must be under a compatible license?
<p>Let's say I wrote a paper which describes &amp; designs a software and its implications, and I license it under the CC BY-SA 4.0. If some else (or me) writes said software, does it need to be in a compatible license (e.g., the GPL v3)?</p>
<p>The license says that derivate works or things made upon said work must be licensed under a compatible license, so I'm wondering if that could apply here.</p>

<p>Copyright protects creative expression, not ideas. To the degree to which the design can be considered a creative expression, the copyleft effects of the CC-BY-SA license would apply and designs that are derived from this design would have to use a compatible license.</p>
<p>But the ideas themselves are not covered by the CC-BY-SA license. Anyone could read the paper and freely implement these ideas in a software, as long as no copyrightable aspects are copied.</p>
<p>What specifically would be protected by copyright would depend on the laws and case law in the relevant jurisdiction. E.g. one jurisdiction might view the design of a class as purely functional and not eligible for copyright, another might see a creative expression in the structure and organization of the API.</p>

copyright software licensing creative-commons gpl