The full rules are listed here:
http://www.project1999.com/forums/sh...d.php?t=132299
"Project 1999 Staff will not be defining what constitutes a camp. Instead, Project 1999 Customer Service Staff will arbitrate spawn disputes on a per-case-basis. We greatly encourage players to find their own resolution to spawn disputes, as the solution provided by the staff will at best be a win-lose situation, and possbily a lose-lose situation. No two decisions, even at the same 'camp', are guaranteed to be the same, as we will take into account multiple factors in making a determination on a 'camp'."
And then, more specifically to your situation:
"That being said, you can absolutely "camp" mobs, and you cannot steal another players 'camp'. In general, if the placeholder or placeholders for a spawn are being killed, that 'camp' can be considered held by the player doing the killing so long as they are keeping the placeholders cleared. You do not necessarily need to be at the spawn point to call it 'claimed' while it is uncontested, however, if someone else wishes to contest the 'camp' you do need to return to the 'camp' and maintain a presence at or very near the spawn(s) in order to hold it. You cannot hold multiple 'camps' if another group wishes to contest one that you are holding. The player holding multiple 'camps' retains the right to choose which 'camp' to give up."
What this means is that you can camp as much as you want, until someone else comes in. Once someone comes and wants some, you must split the camps you are taking. You can keep a camp to yourself, but you must be close to (probably within range of to be safe) the spawn point. While you're there, someone else can go to another mob's spawn point and claim that one as their camp.
You would probably not be considered camp stealing to take roaming mobs. Unless the person is sitting there at the spawn point of the roaming mob, one isn't camping it. Generally (although not exactly), roaming mobs are not camped. So, I do believe you would be in the right to grab some of the roaming Giant Skeletons and killing them, so long as you did not try to steal a mob they had engaged first.