The dictionary file can be build with the indexdict program you'll find in the binaries directory of FreeLing. This program reads data from stdin and indexes them into a DB file with the name given as a parameter.
The input data is expected to contain one word form per line, each line
with the format:
form lemma1 tag1 lemma2 tag2 ...
E.g.
abalanzaría abalanzar VMIC1S0 abalanzar VMIC3S0
bajo bajar VMIP1S0 bajo AQ0MS0 bajo NCMS000 bajo SPS00
efusivas efusivo AQ0FP0