Once again, and for the last time I hope, no GTK2 version is officially available. I uploaded a gtk2 tarball of this release.
Please note that this is not an official gtk2 release, although it is stable.
As a few configuration files differ from the gtk1 version, the default configuration directory is .sylpheed-gtk2. You can copy your old config dir before starting sylpheed-claws, with
cp -r ~/.sylpheed ~/.sylpheed-gtk2
You can also change this default using the –with-config-dir parameter to ./configure.
External plugins should be updated to their GTK2 versions. The plugins with a GTK2 version available have been packaged and are available at the same place.
GPG signatures are available too.