List of notices from Apache licensed software OpenGrok uses:

Apache Lucene
Copyright 2006 The Apache Software Foundation

This product includes software developed by
The Apache Software Foundation (http://www.apache.org/).

The snowball stemmers in
  contrib/snowball/src/java/net/sf/snowball
were developed by Martin Porter and Richard Boulton.
The full snowball package is available from
  http://snowball.tartarus.org/

The Arabic stemmer (contrib/analyzers) comes with a default
stopword list that is BSD-licensed created by Jacques Savoy.  The file resides in 
contrib/analyzers/common/src/resources/org/apache/lucene/analysis/ar/stopwords.txt.
See http://members.unine.ch/jacques.savoy/clef/index.html.

The Persian analyzer (contrib/analyzers) comes with a default
stopword list that is BSD-licensed created by Jacques Savoy.  The file resides in
contrib/analyzers/common/src/resources/org/apache/lucene/analysis/fa/stopwords.txt.
See http://members.unine.ch/jacques.savoy/clef/index.html.

Includes lib/servlet-api-2.4.jar from  Apache Tomcat

The SmartChineseAnalyzer source code (under contrib/analyzers) was
provided by Xiaoping Gao and copyright 2009 by www.imdict.net.

ICU4J, (under contrib/collation) is licensed under an MIT styles license
(contrib/collation/lib/ICU-LICENSE.txt) and Copyright (c) 1995-2008 
International Business Machines Corporation and others
