This repository contains FVWM95 as found at https://downloads.sourceforge.net/project/fvwm95/fvwm95/2.0.43f/fvwm95-2.0.43f.tar.gz with minor adjustments to allow build with modern compilers.
Tested with:
$ uname -biKmoprsv
FreeBSD 13.1-RELEASE FreeBSD 13.1-RELEASE releng/13.1-n250148-fc952ac2212 GENERIC amd64 amd64 GENERIC 1301000 5b12d97f9629e35915bb91fb9145e851f0b437fe
$ clang -v
FreeBSD clang version 13.0.0 (git@github.com:llvm/llvm-project.git llvmorg-13.0.0-0-gd7b669b3a303)
Target: x86_64-unknown-freebsd13.1
Thread model: posix
InstalledDir: /usr/bin
Original README is available as README.hector.