The list editor feature for WSS v3 is enabled in the exact same way as in MOSS 2007. Click the "Site Settings" menu in the upper right corner of the page and select "Site Settings". Then select "Site Collection Features" from the rightmost column. You should see the "Use r.a.d.editor to edit List Items" feature now. Click the Activate button to start using radEditor.
We have already tested the editor with the WSS v3 Wiki Libraries feature and it worked without any problems.