Everson was born in Norristown, Pennsylvania, and moved to Tucson, Arizona at the age of 12. His interest in the works of J.R.R. Tolkien led him first to Old English and then to other Germanic languages. He studied German, Spanish, and French for his B.A. at the University of Arizona (1985), and the History of Religions and Indo-European linguistics for his M.A. at the University of California, Los Angeles (1988). He moved to Dublin in 1989, and was a Fulbright Scholar in the Faculty of Celtic Studies, University College Dublin (1991). He was naturalized as an Irish citizen in 2000. In September 2004, he moved to Westport, County Mayo. He is a Buddhist.
Everson is active in supporting minority-language communities, especially in the fields of character encoding standardization and internationalization. In addition to being one of the co-authors of the Unicode Standard, he is a contributing editor to ISO/IEC 10646, ISO 15924, and RFC 3066. He has contributed to the encoding of many scripts and characters in those standards, receiving the Unicode "Bulldog" Award in 2000 for his technical contributions to the development and promotion of the Unicode Standard.
Everson has been activly involved in the encoding of many scripts in the Unicode and ISO/IEC 10646 standards, including Balinese, Braille, Buginese, Buhid, Cherokee, Coptic, Cuneiform, Cypriot, Deseret, Ethiopic, Georgian, Glagolitic, Gothic, Hanunóo, Khmer, Limbu, Linear B, Mongolian, Myanmar, New Tai Lue, N'Ko, Ogham, Old Italic, Old Persian, Osmanya, Phoenician, Runic, Shavian, Sinhala, Tagalog, Tagbanwa, Tai Le, Thaana, Tibetan, Ugaritic, Unified Canadian Aboriginal Syllabics, and Yi, as well as many characters belonging to the Latin, Greek, Cyrillic, and Arabic scripts.
Together with John Cowan, he is also responsible for the ConScript Unicode Registry, a project to coordinate the mapping of artificial scripts into the Unicode Private Use Area. Among the scripts "encoded" in the CSUR, Shavian and Deseret were eventually formally adopted into Unicode; two other conscripts under consideration are Tengwar and Cirth.
Everson has also created locale and language information for many languages, from support for the Irish language and the other Celtic languages to the minority languages of Finland. In 2003 he was commissioned by the United Nations Development Programme to prepare a report on the computer locale requirements for the major languages of Afghanistan (Pashto, Dari, and Uzbek), co-authored by Roozbeh Pournader, which was endorsed by the Ministry of Communications of the Afghan Transitional Islamic Administration. More recently, UNESCO's Initiative B@bel funded Everson's work to encode the N'Ko and Balinese scripts.