I see there is a thread under development testing for Wikidpad but the thread was started in 2007 and from what I see it doesn't identify what version of Wikipad it's using. See: https://portableapps.com/node/5719
This application is incredibly useful and I really wish it could be made into an official Portable App. It's open-source and it's updated regularly.
Acording to their website, WikidPad is already portable. You just copy the directory with the program, and add copy also the configuration directory inside your user directory. Later, uninstall your WikidPad and run it from your USB.
The last version is 1.9 rc12
Denis J. Navas