1. When I will begin modeling, is there any special preferences I need to keep in mind so they work in the DP2 game?
I guess low vertexes.
2. What file extensions are excepted in DP2?
md2 or skm
5. What are/is GPL?
GPL is a licence that basicly means
open source.
6. What are/is .3Ds?
Thats a model file format
7. What are/is UV mapping?
The process of assigning a 2d plane into a 3d model. Skinning.
8. What are/is .TGA?
Targa file format, its an image.
9. What are/is MD3?
MD3 is the model format for the quake3 engine I think, you shoudnt care about this.
11. What are/is SKM?
Skeletal model format.
12. I read somewhere that something didn't have a md2 exporter. What is a md2 exporter and why is it needed?
MD2 exporter is a program that converts a different format than md2 into md2.
13. Why do some people use one program to make a model, then open the file in Blender (i think i remember this right)?
Because in order to export the models into DP they need to be converted into a format blender can import. Why blender? because its free and has a md2 exporter.
Hope that was helpful.