The development sources are available through CVS at Savannah:
https://savannah.gnu.org/cvs/?group=philosophy
If you are getting the sources from CVS (or change configure.ac), you’ll need to have GNU Autoconf, GNU Automake and GNU Texinfo installed to (re)build. All of these programs are available from https://ftp.gnu.org/gnu/. Their required minimal versions are:
This release was bootstrapped with the following versions:
After getting the CVS sources, and installing the tools above, you can
run, in the top-level directory of the source tree, ‘./bootstrap’
and then ‘srcdir/configure’ to do a fresh build. After
that first time, running make
should suffice. See file
INSTALL.