If you installed the Ubuntu .deb listed on the nightly forum, then that build is for Dapper. It's built using the available libraries from the Dapper repositories. Dapper's repos contain wxWidgets 2.6.1, which is why you see that version listed in the about info. If you are running Edgy, then you probably already have 2.6.3 installed if you installed wxWidgets from the Edgy repositories. In my signature you will see a link to a build for Edgy.