Modifications of Built-In Textures

[starforce84]

I've seen similar posts, but nothing exactly like this, so I hope you don't mind me asking:

I've created a couple new star systems to go along with a science fiction series I created. (This series consists of a whole lot of intricate technical information, personnel dossiers, descriptions of alien races and languages, and a handful of poorly-written stories, all posted on my personal website, not for any sort of profit and where very few people are likely to stumble across, to be honest.)

Since I lack the tools and the know-how, most of the planets in my systems have textures based on "built-in" textures. For example, to make the texture for one of the smaller planets, I took the built-in map of Mercury, horizontally flipped the built-in "asteroid" image, and merged them together. Then I adjusted the hue and saturation to give it a slightly reddish tint.

Now, I'm assuming that's not a problem if I'm using it for my own reference when writing my stories. However, what if I post screen shots of it on my website? Obviously, I'd put a comment about the pictures coming from Celestia, but would I need to say more? What if I eventually wanted to zip up all of my new and altered images and offer them as a downloadable "extra" on my website? Would it be OK if I put a disclaimer in the accompanying readme? (For example, "Textures for the following planets are altered forms of built-in Celestia textures: ..." or even list out what textures and what modifications I used for each planet and moon?)

Any ideas on where I should draw the line?

Thanks!

[selden]

Using screenshots from Celestia might be a problem if they show an Addon which has a restrictive license. Some have a "no commercial use" provision, for example.

Otherwise, Chris has explicitly stated that Addons created for use with Celestia and products created using Celestia (screenshots, movies, etc.) are your own property, to do with as you want. This is similar to having created a program using a compiler: the license of the compiler does not apply to the source code compiled by it or to the binary programs created by it.

Celestia is distributed under the GNU General Public License V2 which you agreed to when you installed it. My understanding is that this means that any derivative work containing components of Celestia (using modified versions of images that were included with Celestia, for example) also must be distributed under the GPL.

However, many of the surface texture images that Celestia uses originated from NASA. NASA products are public domain, although works derived from them need not be. So if you were to modify the original images, rather than the versions included with Celestia, you could do anything you want with them.

[starforce84]

Makes sense to me.

Thank you for your help.

(BTW -- I am using one "Add-On", but I've already received explicit permission from its creator to use it.)