From the site's faq (
http://cgtextures.com/content.php?action=faq) :
Frequently Asked Questions
May I use these textures for free?
Yes, the textures may be used for free in 2D or 3D computer graphics, movies, printed media, computer games and 3D models. When bundled with a 3D model or scene you are allowed to sell it as a package.
No permission is granted to sell or redistribute the textures as a competing product, even when the images are modified. Please do not redistribute or sell textures by themselves, or as texture packs, or as clipart, or as material packs, or as scrapbooking packs.
May I use your textures in printed media?
Yes. You are free to use the textures in printed media, such as magazines, CD covers, DVD covers, books, advertisements, and flyers.
May I use your textures to design a website?
Yes. You are free to use the textures for (commercial) website design if you are creating a unique website (not a website theme, see next FAQ entry).
Can I use your textures to design a website design which I sell to many different people?
No. Textures from CGTextures may not be used in website themes/templates, this is considered reselling textures.
Do I need to pay royalties when I use the textures?
No. CGTextures is not like most stock-photography sites. Textures may be downloaded and used free of charge.
Riccardo