What I did to at least compile:
1. dnld both 0.6 and 0.8 of mcaldrivers
2. use 0.8 and cp -R icap mstore ../libmcal
2.5 copy 0.6 lex files.
3. correct the path to crypt.h
4. correct the Makefile.FreeBSD $< to the filename
Then it compiled.