a little late but the apache solr team announced the version 5 release of the open source search platform. solr now comes as a standalone server (jetty inside) which will be managed via init.d under *nix. old solr 3.* indexes are not supported any longer. also interesting sounds the MoreLikeThis query parser that "allows requesting for documents similar to an existing document". look at the mayor changes or all changes for even more infos. happy indexing!