This is a subset of Etherboot-5.4.2 (actually a CVS version just before the
release of 5.4.3), namely the contents of the src subdirectory.  When upgrading
make sure that you don't accidentially overwrite the Config files (in this
directoty and in arch/i386).  Of course the Etherboot code is still covered by
the GPL.  See the standard Etherboot distribution for the license terms.
Note that this directory tree contains local modifications. One of the biggest
modification is an attempt at making Etherboot build with tools from MinGW
possible. So far this produces an image that doesn't work, because the linker
miscompiles relocations.