Hello!
If you kill someone who has a skin in gun trade, you will indeed pick up his skinned gun, but you won't actually have it, you'll just wield it until you trade guns again or you die. Same thing with every skin on every other gamemode. I'd recommend trying to play deathmatch as you have more chances to pick up Ivory DD44's than in gun trade.
I am unsure whether there are currently unlockable skins or not.
The devs and beta testers are usually found hanging out in Entropy-Server, but some of us play in other places too, you might find some Beta Testers/Devs in Graslu's server and Traitor's Gate Memorial sometimes. Just don't expect to see any of us in 24/7 LTK or Arsenal servers, most of us usually do not play on those, if not all of us.
The community skin is awarded to some people in the community who have been exemplary to contributing some services to the mod, such as Jest from JestServers, who has been providing servers for the game for nearly a decade.
Unfortunately, all users with the community klobb skin are no longer active as far as I know.