Yes seaside is still in active development and there is progress on getting a nice configuration working on Pharo 2.0. Until then you can use our manual build from https://ci.inria.fr/pharo-contribution/job/Seaside-2.0/ to test it.
Seaside works, yet it has not been officially release for 2.0 hence we rely on a gofer script to load all dependencies.
What error? I doubt it's related to seaside. And for the configuration we mostly need somebody to do it :) since the seaside config is pretty big on its own you got to be careful when changing things for a new release.
What's missing to have a "nice" (working?) configuration for Pharo 2.0?