This is directed at everyone and no one in particular. This is my own opinion and I'm not speaking for any other texture pack authors.
Minecraft is a wonderful game, it's also wonderful that Notch has made it so easy to modify the game and plans to make it simpler in the future with support for mods. This has allowed everyone here to enjoy the variety and creativity of dozens or perhaps hundreds of texture packs currently available.
This is your community. You need to respect and protect it for it to continue to grow.
I see more and more frequently that texture packs are using textures from other authors without crediting them or providing links to the original packs and also claiming them as their own. I also see authors offering up "their" textures to others when they have no right to do so. If you include textures from another author then you do not have the right to grant your users unlimited rights to those borrowed textures unless the owner offers you that right.
If you want to continue to see texture packs provided to the community then you need to respect the enormous amount of work that is behind them and offer the authors the credit they deserve and not treat their work as your own. If you see a texture pack using other author's work without crediting them, or inappropriately offering others work up for use you might ask them to correct it and tell them why it's important to respect the other texture pack authors.
No one else may agree with me on this. You may feel this is no big deal. But Minecraft is becoming big. Almost a million copies have been sold. If you don't think that there's a company or corp out there that will soon step in, gather all these works and package them up for sale then you're naive.
I'll be releasing Sanguine under the Creative Commons Attribution-NonCommercial-ShareAlike License. shortly. You might consider doing something similar to protect your own work from corporate poaching and other undesirable uses. http://creativecommons.org/
And if you're taking other's work without crediting them then stop that ****.
Actually, all work you do if its your own, is protected at the moment it is created.
No one can go around gathering these packs and sell them, it would be illegal by law.
Creative commons is a set of different documents to which can help you describe in what ways you let people legally use your work, and while it's not necessary, it's quite helpful if you wish to give out an official rule-set on how people may use what you created.
The respect part you mentioned is a very good point, people need to realize where stuff comes from, users too, respect where parts of a mixing pack comes from, don't take stuff for granted.
Right and not so right.
When you create a work it is automatically copyrighted ( in the US! ) but when you offer it up for free use it is released from your control. Without some stated limitations you no longer have any say over how it's used or wether or not it can be resold.
Setting stipulations on it's use allows you to retain legal rights while allowing certain uses. Even restricting usage is limited in that you have to enforce ( or attempt to enforce ) the limitations that you set in place or you risk losing those rights. And legal battles over usage of a texture pack are unlikely due to costs. But setting these limits at least makes the option possible and may reduce the likelihood that a corp would expose themselves to the legal risk of selling your work. Large coffers equals large liabilities particularly when you can identify profits associated with selling your work.
Primarily I'm concerned with the community taking seriously the effort of the contributors to the game. It's simply polite and the right thing to do. The primary tool for enforcing this behavior is community expectations and pressure, not legal.