Bored of BASIC? No problem!
Due to the Dragon's lack of [ and ] characters, which are quite important in brainfuck, the inputs have been swapped with ( and ).
As for some reason square brackets are in the character set but there are no keys for it on the keyboard!
As the Dragon does not use a standard character set, the values for characters are slightly different. An image of all the available characters for reference can be seen here and on page 136 of An introduction to BASIC programming using the DRAGON.
Included are a disk image: BF.VDK, tape file: bf.wav and binary file: BF.BIN.
To compile, asm6809 is needed, optionally bin2cas and dragondos but these two are not required for building the binary and are just to create the disk and tape images.