FLC OF A BEECH SUPER KING AIR 300 TOOK OFF WHEN A C206 WAS ON SHORT FINAL AND AFTER A C402 TOOK OFF IN THE OPPOSITE DIRECTION TO THE LNDG TFC.

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AS THE CAPT TAXIED TO RWY 18 AT SPRINGDALE ARPT AND CALLED APCH CTL TO PICK UP OUR IFR CLRNC; I RECEIVED THE CLRNC AND WAS TOLD TO HOLD FOR RELEASE AND CALL BACK WHEN READY TO DEPART. REACHING THE END OF RWY 18; I CALLED APCH AND RECEIVED OUR RELEASE. THE CTLR TOLD US HE HAD CE206 TFC ON A 2.5 MI FINAL FOR RWY 18. WE DECIDED WE HAD PLENTY OF TIME TO DEPART AND TAXIED TOWARDS THE RWY MAKING THE ANNOUNCEMENT THAT 'N-NUMBER IS DEPARTING RWY 18; SPRINGDALE.' JUST AS WE STARTED OUR TURN ONTO THE RWY; A CE402 LIFTED OFF ON RWY 36 AND STARTED AN IMMEDIATE R TURN TO AVOID THE TFC LNDG ON RWY 18. WE PROCEEDED WITH OUR TKOF AND HEARD SOMEONE CALL ON CTAF 'DIDN'T YOU GUYS HEAR US?' I STILL DON'T KNOW WHETHER THAT CALL CAME FROM THE CE402 OF CE206. THE ONLY ACFT WE WERE HEARD WAS THE CE206 RPTING A 1 MI FINAL AS WE WERE ROLLING ONTO THE RWY. NONE OF US WERE EVER DANGEROUSLY CLOSE TO COLLIDING; BUT I BELIEVE THIS MESS COULD HAVE BEEN AVOIDED IF THE CE402 WOULD HAVE USED THE PREFERRED RWY -- WHICH IS RWY 18 WHEN THE WINDS ARE CALM OR LIGHT. ALSO; THE CE402 SHOULD NOT HAVE BEEN TAKING OFF INTO TFC LNDG IN THE OPPOSITE DIRECTION -- ESPECIALLY WHEN THE LNDG TFC WAS WITHIN 2 MI OF THE THRESHOLD. BUT FROM NOW ON I WILL BE ALERT FOR OTHER PLTS DOING THINGS THAT MOST OF US CONSIDER UNCONVENTIONAL AND UNSAFE.