A POSIX-compatible operating system with support for BSD signals and sockets. Linux and NetBSD are known to be ok.
The C and C++ development toolset including at least the following utilities:
c++ compiler (Only GCC is known to work at this time)
c compiler (GCC recommended)
The Bourne shell (/bin/sh) (bash is ok, so long as you use version 2.0.4(1) or higher)
The 'ar' utility (as is found in the GNU Binutils package)
Perl version 5.6.1 or higher
An ascii text editor such as vi, vim, emacs, joe, jed, nano, ed, jove, ...
An IRC server compatible with dal4.4.10 such as dreamforge or sor1.3.x (The latter is required for certain features such as autohurt and mode locking to work as they were meant to.
It is also strongly recommended but not absolutely required that you have GNU Autoconf and GNU Automake installed, particularly if you want to tweak your build process, then you do need those.