The development version of LilyPond is designated 2.3
The 2.1.8 version of lilypond is available via the official FreeBSD ports tree.
Simply compile and install using the ports system:
(cd /usr/ports/print/lilypond-devel && make all install clean)
All requirements will be resolved and installed automatically
The latest available FreeBSD port skeleton is lilypond-2.3.4. Until it is committed into the FreeBSD ports tree, it can be downloaded here.
Alternatively the 2.3.4 lilypond portskeleton can be downloaded here: http://foo42.de/distfiles/ports-print-lilypond-devel-2.3.4.tar.gz (md5)Download the port skeleton, remove the old /usr/ports/print/lilypond-devel and untar the ports-print-lilypond-devel-2.3.4.tar.gz in /usr/ports/print/.
Then compile as usual.