> 1. Can it be considered "modified enough" to be considered derivative if it's the original file, plus some Javascript to provide a pop-up notification?
They're altering the functionality of it, fairly substantially imo. I would argue that copyright should protect your IP from being subverted to serve additional, annoying pop-ups.
> Does Comcast violate copyright when it interrupts a television program to show a federally required EAS alert?
In that case Comcast is not altering the contents of the work, it is replacing the content with other content. I don't think that's a violation of copyright at all.
> 3. Captive portals are a well-established instance where a page requested is not what's delivered. No one is accusing them of copyright infringement.
Again, they are not modifying the returned content, they are refusing to display the requested content and returning alternative content.
They're altering the functionality of it, fairly substantially imo. I would argue that copyright should protect your IP from being subverted to serve additional, annoying pop-ups.
> Does Comcast violate copyright when it interrupts a television program to show a federally required EAS alert?
In that case Comcast is not altering the contents of the work, it is replacing the content with other content. I don't think that's a violation of copyright at all.
> 3. Captive portals are a well-established instance where a page requested is not what's delivered. No one is accusing them of copyright infringement.
Again, they are not modifying the returned content, they are refusing to display the requested content and returning alternative content.