Get an Esterel compiler binary for your OS from the old Inria web site.
How to adapt the RedHat Esterel for Debian:
sudo apt-get install ldso libc5 libg++27 tar xzf esterelv5_21.linux.tgz cd esterelv5_21.linux # do magic with the Makefile: it's commented, but poorly. make install
Now you have an Esterel installation. Good luck.
For actually compiling stuff you probably need old versions of GCC and libc development libraries.
sudo apt-get install altgcc libc5-altdev