Please, everyone, learn the terminology. I'm not dinging you or anything, but it is *extremely* confusing, especially to newcomers who read this, when you say "spawncamping is allowed" in dust. It is not.
To recap, and make this clear:
Spawn Camping- it requires someone to be INSIDE the enemy spawn and firing, or hugging a spawn wall and killing them inside the spawn without first being aggressed. Simply put, if you shoot someone in their spawn without them firing at you/teammates, you are spawn camping. If you are inside the enemy spawn, you are spawn camping.
Exit Camping- a subset of spawn camping, as it requires you to be OUTSIDE the spawn area and firing at the enemy within the first few seconds of them leaving spawn. Simply put, you must be outside and engaging the enemy as they leave spawn, but the bodies must fall outside of their spawn area.
Nading spawn (203/RPG/Nade) is a slightly different issue. You are not allowed to nade spawn in any form, but I'll say this now: if I'm running from a to c and have a 203, I'm going to shoot you if you try to take a potshot at me from the ins a exit. Any other people I kill on accident are collateral damage for you shooting at me from your spawn.
Now, on dust, you can exit camp all day long if that floats your boat. Spawn camping is never allowed; firing into spawn is allowed if they are firing at you; and these rules are off if one team is depleted, as it is a safe bet the other is as well and there are afk's hiding in spawn most of the time, so a nade there is needed. As to hugging spawn walls- I've never heard an official ruling, but I don't allow it when I admin because it leads to actual spawn camping. 90% of the time when an INS is hiding at the boxes/wall right when marines come out of spawn they toss nades inside, et.al.