+
+List of external libraries
+--------------------------
+
+A number of external PHP libraries are used to provide basic
+functionality and optional functionality for your system. For your
+convenience, they are available in the "extlib" directory of this
+package, and you do not have to download and install them. However,
+you may want to keep them up-to-date with the latest upstream version,
+and the URLs are listed here for your convenience.
+
+- DB_DataObject http://pear.php.net/package/DB_DataObject
+- Validate http://pear.php.net/package/Validate
+- OpenID by Janrain, http://janrain.com/openid-enabled/
+- PEAR DB. Although this is an older data access system (new
+ packages should use PDO), the OpenID libraries depend on PEAR DB
+ or MDB2.
+- OAuth.php from http://oauth.googlecode.com/svn/code/php/
+ (has been edited to avoid colliding autoload)
+- markdown.php from http://michelf.com/projects/php-markdown/
+- PEAR Mail, for sending out mail notifications
+ http://pear.php.net/package/Mail
+- PEAR Net_SMTP, if you use the SMTP factory for notifications
+ http://pear.php.net/package/Net_SMTP
+- PEAR Net_Socket, if you use the SMTP factory for notifications
+ http://pear.php.net/package/Net_Socket
+- XMPPHP, the follow-up to Class.Jabber.php. Probably the best XMPP
+ library available for PHP. https://github.com/heshanlk/XMPPHP. Note that
+ as of this writing the version of this library that is available in
+ the extlib directory is *significantly different* from the upstream
+ version (patches have been submitted). Upgrading to the upstream
+ version may render your GNU social site unable to send or receive XMPP
+ messages.
+- Facebook library. Used for the Facebook application.
+- PEAR Validate is used for URL and email validation.
+- Console_GetOpt for parsing command-line options.
+- HTTP_Request2, a library for making HTTP requests.
+- PEAR Net_URL2 is an HTTP_Request2 dependency.
+- Michelf/Markdown.php Markdown parser library
+- Mf2/Parser.php microformats2 parser library
+
+A design goal of GNU Social is that the basic Web functionality should
+work on even the most restrictive commercial hosting services.
+However, additional functionality, such as receiving messages by XMPP,
+require that you be able to run long-running processes on your account.
+In addition, posting by email require that you be able to install a mail
+filter in your mail server.