Lemon is maintained as part of SQLite, so to get what you want, you need to clone the SQLite fossil repo. There is one sentence on Lemon's homepage which point

Lemon is maintained as part of SQLite, so to get what you want, you need to clone the SQLite fossil repo. There is one sentence on Lemon's homepage which points that direction, which is very easy to miss. All of the hwaci tools are maintained in Fossil repos and distributed as amalgamations, so that's consistent at least.