So I have a rookie question. When a the GM rolls the dice pool for anything fighting against the PCs and the roll generates any threat. Does the GM spend the threat or the PCs?

The GM. Depending on the scenario it'll be something like causing strain for the PC, setting off an alarm, weapon jam, etc. all handled in narrative.

We have this poor droid who keeps rolling 3 strain. Poor guy falls down each time.

I'm referring to say for example, the GM rolls for a group of stormtroopers to attack a PC and the roll generates threat for the troopers. Do the PC get to decide if say for example the trooper get a setback die next turn or is it still the GM. Just trying to make sure my group plays fare

If the players roll threat or despair then the GM decides how to spend it. If the GM rolls it, then the players decide

It's true the GM is usually the final arbiter on how Threat and Despair rolled by the PC is spent, but nothing is stopping the PCs from making their own suggestions as to what should happen, with the GM using those suggestions if they feel it's appropriate.

Played on game at GenCon (on Thursday I think) where the PC suggested that 3 Threat he rolled be used to disarm his character of his rifle, as the NPC he was attacking had Betrayed him in the past and the PC (a Trandoshan) was so furious that he threw down his rifle and was ready to literally rip his ex-girlfriend to pieces. Talk about your messy break-ups (literally, the room was spattered with gore once the PC was through)

We have this poor droid who keeps rolling 3 strain. Poor guy falls down each time.

If the droid character is generating 3 threat on rolls a lot and the GM is always spending it on strain then the GM might just be doing that to "win". It is powerful and perfectly valid but I wouldn't find it to be very fun. I usually spend it on strain if there is 1 threat or 1 threat left over from using it on something else. With 3 threat they could make some interesting things happen.

You can add setback dice, boost dice, knock the attacker prone, gain a maneuver, do something that gives the target an advantage, or various other things.

It's true the GM is usually the final arbiter on how Threat and Despair rolled by the PC is spent, but nothing is stopping the PCs from making their own suggestions as to what should happen, with the GM using those suggestions if they feel it's appropriate.

Played on game at GenCon (on Thursday I think) where the PC suggested that 3 Threat he rolled be used to disarm his character of his rifle, as the NPC he was attacking had Betrayed him in the past and the PC (a Trandoshan) was so furious that he threw down his rifle and was ready to literally rip his ex-girlfriend to pieces. Talk about your messy break-ups (literally, the room was spattered with gore once the PC was through)

Rolling the 00 on the critical hit chart was the perfect capstone to that :-)

It's true the GM is usually the final arbiter on how Threat and Despair rolled by the PC is spent, but nothing is stopping the PCs from making their own suggestions as to what should happen, with the GM using those suggestions if they feel it's appropriate.

This is pretty much how the campaign Venthrac and I are running works out. The players come up with suggestions for spending threat and the GM is the final arbiter. I find it really makes the game a more fun, cooperative effort.

Agreed. I will always accept ideas and feedback from players where possible. It makes everything better when the players are invested in the story telling