Recently I found out, that the latest Cyberduck-App for Intel-Macs supports two-way autentification for Dropbox, Googledrive and others. I've mailed the developers, if the PowerPC version of Cyberduck could get this feature too (currently there's only/at least webDAV-support). He answered, that they ceased PPC development but since Cyberduck is OpenSource anyone is free to implement that feature into the old PPC-version. Unfortunatly I have no programming skills at all, but maybe someone here has knowledge and fun for that task. It could open a long-term option to get/keep access to main Cloud-providers.