There's an issue with folks making their own sound packs using pre-existing sounds??
I have no problems with folks re-mixing pre-existing sound packs. Most times I will love the gun sounds but hate the engine looping, or hate the damage/explosions and all the flaps/gear/etc but I want to use those engine sounds.
I have probably been through every sound pack out there, and my current "sounds" setup has a good mix from all of them, including a few sounds not in any! (scrounged myself up some gun sounds here and there).
If I were to compile it into a pack, I sure as HELL put a lot of effort into it, including hours upon HOURS of in-game flight where I tested out every permutation of the sounds, and said "no, I really hate that" or "yes! finally that's perfect!" and so on.
Anybody that does this DEFINITELY put their own work into it. They didn't create the sounds themselves, but they put a lot of their own tastes and likes/dislikes into the choices on what is included.
However, I would like to make one comment. I've mixed and remixed so many packs I can't say what files I got from which packs. If I ever wanted to make a .ZIP of my "sounds" directory I'd love to give credit where it's due, but I honestly couldn't remember which files came from whom! I think that just goes along with mixing so many different sounds and different sound packs. It's nearly impossible to keep track of after-the-fact.
P.S. My current sound mix took several months to get right and includes a few sounds from almost every pack out there. I can't begin to thank the folks that put them out there enough. Somebody puts a sound pack out that I hate 100% and I'll still thank them -- because they give me a choice on what to mix in. I don't have to like it, but they give me more options.