Welcome to the Xapian project website.
Xapian is an Open Source Search Engine Library, released under the GPL v2+. It's written in C++, with bindings to allow use from Perl, Python, PHP, Java, Tcl, C#, Ruby, Lua, Erlang and Node.js (so far!)
Xapian is a highly adaptable toolkit which allows developers to easily add advanced indexing and search facilities to their own applications. It supports the Probabilistic Information Retrieval model and also supports a rich set of boolean query operators.
If you're after a packaged search engine for your website, you should take a look at Omega: an application we supply built upon Xapian. Unlike most other website search solutions, Xapian's versatility allows you to extend Omega to meet your needs as they grow.
The latest stable version is 1.4.0, released on 2016-06-25.
The latest old stable version is 1.2.23, released on 2016-03-28.