CFLs generally run pretty cool.
Put it this way: If you can put your hand comfortably right on the reflector or right next to (or even touching) the light, its not going to be hot enough to start a fire.
Fires are usually started if there is either a short circuit (eg water gets into the electrical system causing sparks), or if you are drawing too much power through a faulty circuit breaker/fuse system, causing it to overheat. So long as its wired correctly, 100 watts of CFL shouldn't be any more likely to cause a fire than a conventional 100 watt light bulb.