I am the official maintainer of FreeLarn.
Compiling Larn from source will require a C++11 compiler as a minimum plus ncurses/pdcurses. See the 'build' folder for makefiles. Compilation should be without a single warning. I treat all warnings as errors (and therefore bugs).
FreeLarn is a direct descendent of the original Larn, that has been mostly (approx 91%) rewritten into C++11 with many additions and features that many now consider a variant.
In 2015 I took the 12.4 Alpha release, fixed it and released it. Later on I rebased my changes onto 12.4.4. Years went by and change after change happened. I dislike the idea of just because something is old, don't change it, Larn will carry on being developed, not just maintained.
Initially, development stopped in March 2018 due to the negativity expressed by some people about my changes. I genuinely missed working on it and enjoy playing it, so I picked it back up.
I'm generally following the Linux kernel coding style, going function by function and rewriting them to classes and / or templating them to modern equivalents but still be almost drop-in replacements for the old stuff. Usually each function rewritten gets about 1 hour of testing and fine-tuning.
Feel free to raise Issues or PR's if you have something to add/fix.