All software produced by The Apache Software Foundation or any of its projects or subjects is licensed according to the terms of the documents listed below.
Apache License, Version 2.0 (current)
http://www.apache.org/licenses/LICENSE-2.0 (TXT or HTML)
The 2.0 version of the Apache License was approved by the ASF in 2004. The goals of this license revision have been to reduce the number of frequently asked questions, to allow the license to be reusable without modification by any project (including non-ASF projects), to allow the license to be included by reference instead of listed in every file, to clarify the license on submission of contributions, to require a patent license on contributions that necessarily infringe the contributor's own patents, and to move comments regarding Apache and other inherited attribution notices to a location outside the license terms (the NOTICE file).
The result is a license that is supposed to be compatible with other open source licenses while remaining true to the original goals of the Apache Group and supportive of collaborative development across both nonprofit and commercial organizations. The Apache Software Foundation is still trying to determine if this version of the Apache License is compatible with the GPL.
All packages produced by the ASF are implicitly licensed under the Apache License, Version 2.0, unless otherwise explicitly stated. More developer documentation on how to apply the Apache License to your work can be found in Applying the Apache License, Version 2.0.
Apache License, Version 1.1 (historic)
http://www.apache.org/licenses/LICENSE-1.1
The 1.1 version of the Apache License was approved by the ASF in 2000. The primary change from the 1.0 license is in the 'advertising clause' (section 3 of the 1.0 license); derived products are no longer required to include attribution in their advertising materials, but only in their documentation.
Individual packages licensed under the 1.1 version may use different wording due to varying requirements for attribution or mark identification, but the binding terms were all the same.
Apache License, Version 1.0 (historic)
http://www.apache.org/licenses/LICENSE-1.0
This is the original Apache License which applies only to older versions of Apache packages (such as version 1.2 of the Web server).