Paint.net and GIMP are 2D graphic editing programs, not texture generators (like Wood Workshop and it's "commercial" cousin, Genetica); there's a difference. A wood texture created in the GIMP would be a bit more difficult to make, versus a program that generates a seamless wooden texture based on a few pieces of input from the user.
However, if the texture generating program was something you had to buy (like the full Genetica, or a few Alien Skin filters), then it would be worth some money (depending on quality, etc.).
Exactly what should I "re-word"?
Here's the link to my free
Wood Texture Pack. It's been downloaded quite a bit from both my site, the3DStudio.com and Turbosquid. I'm not saying that there isn't a market for good wood textures; but they should be something special coming from a freely distributed program.
-Keith