The keyboard is designed for people who use the regular U.S. keyboard heavily, but occasionally need to type other Latin letters (especially accented ones), symbols, and punctuation. In particular, the keyboard supports the Windows-1252 (U.S. and Western Europe) repertoire, as well as almost every Latin letter in Unicode.
This keyboard handles only the extended Latin alphabet. If you want a regular Greek, Russian Cyrillic, or full IPA keyboard, I recommend the standard Microsoft Greek keyboard, the Russian Phonetic YaWert keyboard, and the Benct X-Sampa keyboard respectively.
If you want a Moby-style keyboard driver for the U.K. physical keyboard, use my Whacking Latin keyboard driver instead.
There are two basic ways to type characters other than the regular ASCII set. A few characters are directly typed by holding down AltGr and pressing another key. For example, to type the character æ, simply type AltGr+a. As you might expect, the capital version Æ is typed as AltGr+Shift+a. However, the great majority of characters are typed using AltGr plus some key, followed by another key that doesn't use AltGr. For example, the letter a with diaeresis (ä) is typed with AltGr+; (that is, AltGr plus semicolon) followed by a, or by A if you want the capital a with diaeresis (Ä).
Combinations like AltGr+; are known as "dead keys", because they appear to be dead when you type them; you need to press a following key to actually input a character. The current version, C, of the Moby Latin keyboard has a total of 33 dead keys. 23 specific accent marks and modifying strokes are provided, as well as curly quotation marks and other punctuation, math symbols, Roman numerals, fractions, arrows, pointing hands, math Greek letters and symbols (no accents), obscure Latin letters, and a subset of IPA letters needed for English. (Some math symbols were taken from the space cadet keyboard.) Some of these dead keys are typed using AltGr+Shift, which makes them a little awkward to type, but they are intended to be as easy to remember as possible.
This keyboard and the associated documentation are Open Source, and may be freely copied and modified. The license terms for both is the MIT License. Use, share, and enjoy!