The managed BZIP2 code included in Ionic.BZip2.dll and Ionic.Zip.dll is modified code, based on Java code in the Apache commons compress library.
Apache Commons Compress ( http://commons.apache.org/proper/commons-compress/ ) is provided under the Apache 2 license:
Apache Commons Compress
Copyright 2002-2014 The Apache Software Foundation
Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License athttp://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
Many thanks to Julian Seward for the original C implementation of BZip2 ( http://www.bzip.org/ ).