I&#x27;m a law student but not an expert, and I haven&#x27;t researched the caselaw (yet?).  Rcthompson, I apologize for taking this opportunity to go way beyond your question (see below).  [This also reflects my assumption that you are coding within the US.  And also this is not legal advice, merely hypothetical musing.]<p>Whatever you write, if copyrightable, automatically achieves copyright protection when fixed in tangible form - and you automatically obtain authorship rights. That gives you the right to grant licenses for any of the rights you&#x27;ve obtained (including to produce derivative works). Swift&#x27;s license (<a href="https:&#x2F;&#x2F;swift.org&#x2F;LICENSE.txt" rel="nofollow">https:&#x2F;&#x2F;swift.org&#x2F;LICENSE.txt</a>) allows you to modify the license of your additions (your right under federal law anyway), but not the sections you didn&#x27;t author.<p>I mean... I can see it cutting both ways. On its face, it&#x27;s a very fair system - you can use whatever you want but only own whatever you wrote. What becomes problematic is if companies (realistically) with wide distribution nets grab open-source code, modify it slightly, alter the license of the bundle and resell it. I know that&#x27;s not a new phenomenon.<p>Another concern I see is if libraries or maybe files or something have proprietary names, then in theory you&#x27;d require an express license from the proprietor (in this case basically Apple).<p>I was concerned I didn&#x27;t understand the basic question that prompted my response, which was from rcthompson, but he reframed it: commits 1 to n-1 have sort of Schrodinger&#x27;s Cat licenses. They have copyright protection (regardless of any of this). And that grants you the right to control licensing of those rights (reproduction, public display, derivative works, etc.). But I don&#x27;t see why you couldn&#x27;t retroactively apply whatever you want. The Swift license applies itself, if you don&#x27;t specify otherwise, upon submission of your work to the licensor (I guess per notice requirements). Until then it&#x27;s unclear. However, federal copyright protections and state common and statutory laws would also apply (and would basically grant you the right to control licensing).