No matter what, when you breed something that is directly related to something else (mother-son, brother-sister, father-daughter, etc), then it is inbreeding.
However, inbreeding is not in and of itself a bad thing.
It's important to note that inbreeding does not *cause* bad genes - it just identifies where they are. So, when inbreeding is totally ignored and all a breeder does is breed unrelated animals, hidden undesirable genes just keep being passed around. Then, when the breeder DOES inbreed, ohmigawd bad genes! Inbreeding must be bad, then!
This is much more apparent when breeding mammals than reptiles, but it can still be applied to an extent. When your inbreeding results in undesirable characteristics, try to breed out those characteristics. This means that due to the long generation gap in ball pythons (about 3 years, average, for a baby (female) to be able to breed!) you're going to end up with a breeding plan that spans a couple decades.
Good dog breeders, or horse breeders, have breeding projects that they've been working on for years and have planned out for another twenty years.
The link I'm including with this is to a page talking about rat breeding, but the concepts about inbreeding are the same. It's a good site that's easy to understand, and will hopefully answer your questions more. 
Just in case the blue link you can click doesn't pop up, here's the URL:
http://carawatha.tripod.com/inbreeding.htm
Hope some of that helps!
~jenny
Good info.
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
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