Can you opt out of a readied action if you no longer wish to perform the action? This can either be because you wish to conserve resources or because the target is not what you intended.
The rule states "anytime before your next action, you may take the readied action in response to that condition." (emphasis mine)
I've run into GMs who make me take it no matter what. I.e. I ready an action to shoot the next thing to run around the corner. The rogue in my party comes running past, the GM says I have to take the shot (even though I'd rather not shoot the rogue I've been adventuring with for the past several levels).
Most GMs I've dealt with give you the option to let your readied action go off or not, but if you're having issues like that, perhaps you should make sure you're more specific with your wording.
If your GMs are taking such a literal interpretation to your wording, perhaps you should make sure you can't be misinterpreted.
"Ok, I'm going to ready an action to shoot the first thing that comes around the corner that isn't a party-mate, an innocent bystander, a slave we're trying to rescue, a faction mission goal (unless they need to die), a merchant, a bunny rabbit, or anyone else that isn't obviously an enemy."
You could also point out the fact that in PFS there is no willing/knowing PVP allowed, and since you obviously recognized your Rogue friend, you couldn't knowingly shoot them.
Use this example:
PC Wizzy Wizard has highest initiative. He readies a magic missile for the event that the enemy leader becomes visible.
Cardinal Anthrax, leader of the Creeping Black Brigade uses a free action to declare he wishes to discuss his surrender. Then he uses a move action to stand up, becoming visible.
Is it in any way reasonable to disallow Wizzy the option to forgo his attack or is Wizzy not literally forbidden to accept Anthrax' surrender?
No. If you do not take your readied action, you are penalized by losing your action for an entire round. There's no need to penalize you further by removing your character's ability to react to changing circumstances.
The Guide to PFS says "In short, you can never voluntarily use your character to kill another character — ever. Note that this does not apply to situations where your character is mind-controlled by an NPC and forced to attack a fellow Pathfinder."
So it sounds as if, in PFS play, you simply won't be able to cast that fireball if a party member is in its area.
As far as I have got it (I read the PFS forum but so far I haven't had any PFS event near here):
- your character spell/area effect attacks will damage friends that are in the AoE or that are hit by splash damage;
- you can't willingly targets friends or include them in the AoE of your attacks unless they give you permission;
- without their permission you aren't allowed to use a AoE or targeted attack that will damage a friend.
So, no, it is not WOW spell effects, it is only a safety measure to stop people that act jerks when they play with strangers.
Yes, as the above poster said, most PFS GMs seem to understand the rule such that any harmful effect is fine as long as it's with the permission of those who could potentially be harmed. The no-PvP rule is in place to give players veto rights against jerks who might harm them with reckless behavior.
In no circumstances should it happen that an effect otherwise takes place but PCs are excluded from it due to the no-PvP rule. That would give a huge boost for characters using effects with possible collateral damage. Trying to keep your allies out of your fireballs is part of the life of a blaster wizard, and PFS shouldn't change that. If the no-PvP rule is invoked, the whole action is prevented.