There has been a trend, in recent days, of moving towards providing tweets under various licenses; most prominently, Creative Commons Non-commercial Sharealike. While I thoroughly approve of strong copylefting, there were some issues that struck me as incredibly problematic with this stance and I would like, in this post, to briefly explore a few of these areas.
1.) Copyleft depends upon Copyright
In order to be able to license something, you have to hold the copyright to it. Brock Shinen, an intellectual property lawyer, has written an informative website focusing upon whether a tweet is copyrightable. While not formal legal advice, Brock concludes that although “a protectable tweet” could exist “in theory”, “I have read hundreds if not thousands of Tweets and have yet to read one I believe would be protectable, but the possibility exists. The question is not: Are Tweets Copyrightable. The question is: Is This Tweet Copyrightable.”
In short, if a tweet is expressing something not covered by copyright law (facts, titles, slogans, short phrases, non-original material), the fact that you wrote it does not mean that you own exclusive rights to it.
Now, as Copyleft depends upon copyright for its enforcement (why do you think the GPL requires a copyright notice at the top of every file of code?), if the material you are tweeting comes with license conditions, it MUST be copyrightable and copyrighted. Although a copyright notice is not required (an author's name is sufficient), if your tweet is not copyrightable, you don't have a leg to stand on.
Assuming, for the moment, that tweets are, in general, copyrightable and copyrighted (as the determined copylefter would have it), Twitter's primary functionality revolves around the ability to re-tweet other peoples' posts. This is all well and good, but has some fundamental problems for the determined copyleftist. First off: the fundamental assumption behind copylefting your tweets is that they are copyrighted and you want others to respect the copyright (and left) on your tweets. If, therefore, you re-tweet somebody else's post that has no explicit license, are you not (by your own assumption) violating their copyright?
Even more importantly, though, by applying a Copyleft license to your tweets you are preventing yourself from participating in a vital portion of Twitter's functionality. By the standards already mentioned, if you were to re-tweet another person's copyrighted tweet and, thereby, force their work under your own license, this would be a gross re-licensing violation. If you copyleft your tweets, you can only re-tweet posts under a compatible license.
3.) Visibility of Copyleft notice
Twitter only archives 3200 tweets (as far as I know). If you specify that you are copylefting all future tweets, there will come a time when that notice will no longer be visible anywhere on your timeline. Although technically (under the aforementioned points), nobody should be reusing your tweets for anything, because they are copyrighted, if this permission notice isn't visible, I'm not sure as to the enforceability of the license.
These are just thoughts that occurred to me and I would be extremely interested in feedback and thoughts from anybody else who has thought about these issues.