I wrote lemon in the late 1980's on a Sun4, while a graduate student. There was also a program called "lime" that generated an LL(1) parser, but I've long since lost that code.

Lemon was intended as a yacc-replacement. The advantages of lemon over yacc are that lemon has a less error-prone syntax (it uses symbolic names rather than $1, $2, etc), and that lemon generates a reentrant and thread-safe parser. (At the time, yacc/bison parsers were neither reentrant nor thread-safe. I don't know if that has been fixed in the intervening decades.)

Lemon has always been open source. But it languished with little attention for 10 years until I used it to generate the parser for SQLite. Then suddenly people started to notice and use it.

Lemon does not have a separate version control system. The source code to Lemon (a single file of C plus a template file for the generated parser) are part of the SQLite source tree.