This site puts the maximum at 4296 alphanumeric characters.
As a test, I took
your post with 2439 characters and created this with
qrencode:
That's pretty amazing, the problem there is that software you mentioned is for linux. I would need a windows tool that could do the same type of thing. The qrcode software I have was able to read your huge qrcode and decode it into text but when I tried to encode the same text into a qrcode, it wouldn't work since it only allows up to 1024 characters apparently.
Looking at qrencode website (
https://fukuchi.org/works/qrencode/), there are windows port such as
http://code.google.com/p/qrencode-win32/, but it's a bit outdated. Besides, there are many QR code software/library on Windows.