Apache Lucene

General info:

Apache Lucene is a high-performance, full-featured text search engine library written in Java.

Points of commendation:

• It has a categorized Readme documentation that guides the reader to its appropriate section.
• It has a lot of contributors which means this project is a good example for a team cooperation.
• Since it is an open-source project, everybody can open an issue about a problem they encountered in the project and the contributors can guide them about their problem.
• Even though its labeling system lacks colors, It has a decent labeling system which is descriptive enough

Points for consideration:

• It does not have a wiki section which is handy for quick team documentation

Here is the link of Apache Lucene