I don't think I've seen any general notice about this, though people may have mentioned the site recently: the web site for everything you wanted to know about abc notation has moved, so update your bookmarks

http://abcnotation.org.uk/
(which actually gets you to http://www.walshaw.plus.com/abc/)

From the home page:

introduction

abc is a language designed to notate tunes in an ascii format. It was designed primarily for folk and traditional tunes of Western European origin (such as English, Irish and Scottish) which can be written on one stave in standard classical notation. However, it has been used for many other types of music and, for example, Steve Allen has coded Beethoven's Symphony No. 7, Movement 2 in abc!

Since its introduction at the end of 1991 it has become very popular and there now exist many abc software tools (for Windows, Mac, Palmtop and UNIX platforms) which can read abc notation and either process it into staff notation or play it through the speakers of a computer.

One of the most important aims of abc notation, and perhaps one that distinguishes it from most, if not all, computer-based musical languages is that it can also be read easily by humans. In other words, with a little practice, it is possible to play a tune directly from the abc notation without having to process and print it out. Even if this isn't of interest, the resulting clarity of the notation makes it very easy to notate tunes. In addition, the ability to write music in abc notation means that it can be easily and portably stored or transported electronically, hence enabling the discussion and dissemination of music via email.

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~ Becky in Tucson