Unfortunately, Adam Salter passed away in 2009. Those who knew him know what an amazing guy he was, and what an excellent Rails programmer he was. His passing is a great loss to the Rails community.
Karl Varga has taken over development of SitemapGenerator.
The canonical repository is http://github.com/kjvarga/sitemap_generator.
Issues should be logged at http://github.com/kjvarga/sitemap_generator/issues.