What is Apache Licence?

Apache License helps developers build open source, collaborative, durable and reliable software products.
Any software product produced by companies or individual developers is donated and licensed by the Apache Software Foundation. It allows users to use the licensed software for any purpose.
All packages produced by ASF (Apache Software Foundation) are implicitly licensed by Apache License 2.0 unless otherwise stated.
Licensed software is free to use and there is no distinction for personal or commercial use.
You may modify and distribute existing Apache code, taking into account the following conditions. Even if each line of licensed code is changed, the result is based on ASF’s licensed code. Edited code may be distributed under a new license, but ASF must approve use of the software.
- You must also forward a copy of the original code to anyone to whom you distribute the edited or derived code.
- You should leave notes in the edited places of the edited files.
- You must retain copyright, patent, trademark, and attribution notes in source format on files.
- Derivative works of the license must contain a note file named “NOTICE” as in the example below.
NOTICE File Example
NOTICE File Example: https://www.apache.org/licenses/example-NOTICE.txt
You can set your own copyrights for changes and provide different license terms. In case the changes made are shared with Apache again, other software developers can benefit from the new structure.
Apache License Versions
Apache License 2.0 was approved by the Apache Software Foundation in 2004 and is the last Apache License still in effect. Before Apache License 2.0, there are 2 more Apache Licenses.
Apache License 2.0 : It was approved by ASF (Apache Software Foundation) in 2004. Current and valid version.
Apache License 1.1 : It was approved by ASF (Apache Software Foundation) in 2000.
Apache License 1.0 : Original first Apache License version.
Applying the Apache License to the Software
You can also license your own software with Apache.
Add a file named LICENCE to the project file and add the license copy below. Consider adding the file NOTICE as well.
You can also add the following code to the content of all files in the project, instead of the LICENSE file, with a comment at the top. Replace the copyright field “Copyright [yyyy] [name of copyright owner]” with your own information.
Copyright [yyyy] [name of copyright owner]
Licensed 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 at
https://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.
There is also a shorter variant that you can use depending on your preference.
Copyright [yyyy] [name of copyright owner]
SPDX-License-Identifier: Apache-2.0
Details for licensing the software: https://www.apache.org/legal/src-headers.html
Source:
https://www.apache.org/licenses/LICENSE-2.0
https://www.apache.org/foundation/license-faq.html