Coumerelli, the folder-actions tricks should work with all OS X versions that support folder actions... I'd imagine that includes 10.5.

The command-line stuff should work with all versions of OS X, can't see any reason it wouldn't.

I've also found a GUI interface to the Tesseract OCR script for 10.5 and later: http://download.dv8.ro/files/TesseractGUI/

Keep in mind that the basic Tesseract script takes uncompressed TIFF files only. So, whatever your scanner produces, you'll need to convert to uncompressed TIFF. The folder action trick does that when fed a .png.

There are ways to make Tesseract work with other formats if you really need to, and you can find those with a little googling and implement them with more command-line fussing. More trouble than it's worth, IMHO, given how easy it is to do uncompressed TIFF conversions under OS X.

One thing I've found is that the folder action for the OCR doesn't like to be fed multiple files all at once. It seems to prefer to have the first file converted and no other folder actions underway. This is no problem if your intent is to have it auto-OCR images as they come from the scanner (and any conversion process). But if you drag a whole bunch of TIFF files into the folder-action-enabled "OCR me" folder, some of the files will be missed. This appears to possibly point to a bug in the folder-actions mechanism.