Since I have moved on to other projects, I hereby release the JavaScript code (http://canvaspaint.org/paint.js) into the wild: If this code, messy as it is, is of any use to you, feel free to take it.

This expressly does not include images, cursors or any other intellectual property, the rights to which I do not own myself.

Firefox 3 will provide these unstandardized, experimental methods:
mozDrawText();
mozMeasureText();
mozPathText();
mozTextAlongPath();