Here is how you can install the current development version (not yet released, expect issues) of the wikipedia and the pt_assistant JOSM plugins:
F12).Expert mode in the bottom left corner of the preferences dialog is checked.Plugins tab. Click on Configure… in the bottom right corner.

Add in the new dialog and enter the URL https://josm.github.io/wikipedia/pluginMasterSnapshots and confirm with OK.Download list, you have two new plugins in the plugin list: wikipedia-dev and pt_assistant-dev. You can install these and they are updated like the “normal” JOSM plugins too.Note: Please make sure that you don’t have both the dev and the non-dev version (e.g.
wikipediaandwikipedia-dev) installed at the same time! This would probably lead to conflicts.
Another note: The
pt_assistant-devplugin will always be redownloaded whenever you check for plugin updates. Thewikipedia-devplugin is only redownloaded when there is actually a new version available on the master branch.