Zwiki is about 10,500 lines of Python, with about 24,000 lines of total code if you consider templates and dtml and other non-python code.
See ZWiki:ZWiki for more information.
Line counts were done on ZWiki 0.11.0 on Debian, like this:
cd /usr/lib/zope/lib/python/Products/ZWiki find . | grep py$ > /tmp/temp cat /tmp/temp | xargs -n1 cat > /tmp/concat wc /tmp/concat find . | grep -v .pyc > /tmp/temp cat /tmp/temp | xargs -n1 cat > /tmp/concat wc /tmp/concat
ZWiki:LinesOfCode confirms the 10,500.