FontForge1 is an outline font editor written by George Williams. FontForge can be used to create or edit Postscript, TrueType, OpenType, CID-keyed, multi-master, CFF, SVG and BDF fonts. The program will also permit you to convert fonts from one format to another.
Here the Arphic Unicode Ming font is shown being edited. Arphic Technologies of Taiwan generously released a set of Big5 and GB2312 fonts under an Open Source license. Arne Goetje of the Debian project in Taiwan is now using FontForge to create Unicode-encoded fonts for use on Linux based on the glyphs from the legacy Arphic fonts2. He is also adding new glyphs for the Bopomofo extensions for Hakka and Minnan added to Unicode 4.0, as well as Han characters in the Hong Kong Supplemental Character Set (HKSCS).
The Taiwan Debian CJK font project is just one example of many Open Source font development projects made possible by the existance of this free/libre font editor.
1. Fontforge, http://fontforge.sourceforge.net/.
2. Arphic CJK fonts to Unicode project, http://debian.linux.org.tw/pub/3Anoppix/people/arne/.