The dev86 package provides an assembler and linker for real mode 80x86
instructions. You'll need to have this package installed in order to
build programs that run in real mode, including LILO and the kernel's
bootstrapping code, from their sources.

The dev86-devel package provides C headers need to use bcc, the C
compiler for real mode x86.

You should install dev86 if you intend to build programs that run in real
mode from their source code.

Note that you don't need dev86-devel package in order to build
a kernel.