There is exactly one small dependency that the SolrJ jar has to lucene-core and that is indirectly via ConcurrentLRUCache which is in common/util. SolrJ doesn't even use this cache but it's there any way. Attached is a patch for the move. It also removes the lucene-core dependency that the SolrJ maven pom.xml has on lucene-core.
Steve Rowe agrees: