The code was exported to GitHub, to which I assume is the author's account (rsc):
https://github.com/rsc/qr
However, I'm not familiar with go and all I see there, is what looks like a plain QR encoding library.
There is also code for the web server:
https://github.com/rsc/swtch/blob/master/app/blog/qr.go
Again, I don't know how to dig further to find the source of the qrweb module.
Any ideas?