The idea is to create a CGI script that when given the layout of a chess board in Forsyth Notation will create an image of the chess board.
I chose to implement it in Perl using PerlMagick for image processing functions. Download the source.
Also, in the end, I decided to make the query string use a slightly modified version of the Forsyth Notation, using full stops (.) instead of soliduses (/). This is because the solidus has a special meaning in URLs.
Update: it now also accepts %2F (URL-escaped solidus) as a seperator.