If one modifies and distributes intellectual property based on a Creative Commons licensed work, do they have any claim to their modification?
<p>Suppose someone named Alice makes a free-to-play game called "Tubbytown" and releases it under the creative commons license "Attribution-NonCommercial-ShareAlike," which from the Creative Commons website says</p>

<blockquote>
  <p>This license lets others remix, adapt, and build upon your work non-commercially, as long as they credit you and license their new creations under the identical terms.</p>
</blockquote>

<p>Now suppose the game is a big hit, and everyone is loving it, especially Bob, who loves it so much that he starts to develop expansions and enhancements to Tubbytown, all for free of course and in full compliance with the original license.</p>

<p>But Alice has been developing her own enhancements, and they're pretty similar to Bob's. They both identified similar painpoints in the game, and they both patched them, but Bob released his patch first. Does Bob have any claim over his enhancements, even though he isn't allowed to sell them? Would Alice be prevented from coming up with enhancements to her own game if other people could prove they thought of and released the idea first?</p>

<p>Now, I'd like to take this one step further. Let's imagine that Bob came up with some very cool and unique enhancements to Alice's game that she had not thought of, and he releases them for free because he is restricted from selling them. Could Alice outright claim Bob's "Adapted Material" because he developed it on her original work?</p>

<p>I hope this is clear enough.</p>

<blockquote>
  <p>Alice has been developing her own enhancements, and they're pretty similar to Bob's.</p>
</blockquote>

<p>Neither Alice nor Bob has copied the other's enhancements, so neither has violated the other's copyright in the enhancements.  Whether that could be proved in court is another matter, of course, but since the original work is licensed under creative commons the question unlikely to arise in court.</p>

<blockquote>
  <p>Would Alice be prevented from coming up with enhancements to her own game if other people could prove they thought of and released the idea first?</p>
</blockquote>

<p>No.  Copyright does not protect ideas.  It only protects a particular expression of those ideas from being copied.  Theoretically, if two authors come up with identical 500-word descriptions of something and can establish that each did so independently, neither has a claim against the other.  The practical problem there, of course, is that it would be impossible to prove such a thing.</p>

<blockquote>
  <p>Could Alice outright claim Bob's "Adapted Material" because he developed it on her original work?</p>
</blockquote>

<p>Assuming that in publishing his adaptations Bob followed the terms of the creative commons license with respect to the original work, Alice's only claim would be that he copied <em>her adaptations</em> without following the terms of the license.  If Bob can show that he did not do so, her claim would fail.</p>

<p>In a comment, you wrote:</p>

<blockquote>
  <p>Suppose Alice went ahead and intentionally, somehow provably ripped off Bob's "Adapted Material" because she liked the content so much, does Bob reserve any rights on his adaptation, or is Alice able to commercialize the work that Bob did in extending her original work?</p>
</blockquote>

<p>If we assume that Bob complied with the license of the original material, we know that he licensed his adaptations under "the identical terms," so Alice would be able to use Bob's adaptations under those terms for non-commercial purposes.  Since the assumption here is that Alice <em>provably</em> copied something of Bob's, I think it is fairly clear that she would be liable for damages if she exploited that material commercially without paying royalties.</p>

intellectual-property creative-commons