Do you happen to know what altitude firefighting aircraft fly at when they drop? It would seem that 500' AGL would be on the high side if you expect the fire suppression material to hit anywhere near the target site in any reasonable level of concentration. I know nothing about the subject matter though, so that could be a bad assumption.
Pilots check NOTAMs before takeoff to see if there's anything going on they need to know about. There's an FAA search engine for NOTAMS [2], and it will accept lat/long coordinates. This is the sort of thing that the basic training and exam for drone operators must cover - check the NOTAMs before flight.
For the San Bernandio Mountains fire, there's a NOTAM:
ZLA LOS ANGELES (ARTCC)PALMDALE, CA.
!FDC 5/6263 ZLA CA..
AIRSPACE SAN BERNARDINO, CA..
TEMPORARY FLIGHT RESTRICTIONS WITHIN AREA DEFINED AS 3 NM RADIUS
OF 340927N/1171437W (PARADISE VORTAC PDZ030020.2) SFC-6000FT. TO
PROVIDE A SAFE ENVIRONMENT FOR FIRE FIGHTING. PURSUANT TO 14 CFR
SECTION 91.137(A)(2) TEMPORARY FLIGHT RESTRICTIONS ARE IN EFFECT.
USFS TELEPHONE 909-383-5651 OR FREQ 123.775/STERLING FIRE IS IN
CHARGE OF THE OPERATION.
LOS ANGELES /ZLA/ ARTCC TELEPHONE 661-265-8205 IS THE FAA
COORDINATION FACILITY.
EFFECTIVE 1506260700-1507010700
For a pilot, "busting a TFR" (entering an area with restrictions like that) usually means a 30-90 day grounding. For something like actual interference with aerial firefighting, the penalties would be much higher.
There's an app for this.[3] Small drone operators might use a dumbed-down version which just gives you anything applicable to low-altitude operations near your current location.
The sky has many users and traffic rules. Drone operators have to be very aware of this.
[1] http://www.nifc.gov/nicc/logistics/references/Airspace_Guide... [2] https://pilotweb.nas.faa.gov/PilotWeb/ [3] https://itunes.apple.com/us/app/notams/id354048843
There may be a "micro UAV" (< 2Kg) category for toy-sized drones, with fewer restrictions. That's still being discussed. A study on consequences of a drone collision indicate that large aircraft could probably survive collisions with 2Kg drones without serious risk to the aircraft.[2] That doesn't mean no damage, it means the aircraft can land safely. Any jet engine which takes a bird strike gets a major overhaul, which costs upwards of $100K.
[1] https://www.faa.gov/regulations_policies/rulemaking/media/02... [2] http://www.uasamericafund.com/assets/micro-uav-safety-analys...