XAMPP combines many different sofware packages into one package. Here's an overview of all packages.
Many thanks to the developers of these programs.
Apache HTTPD
mod_autoindex_color module
FileZilla FTP Server
Mercury Mail Transport Agent
OpenSSL
SQLite
The Webalizer
msmtp (a sendmail compatible SMTP client)
MySQL
PrimeBase XT Storage Engine for MySQL
PHP
eAccelerator extension
Xdebug extension
Ming extension
PDFlib Lite extension
PEAR
phpMyAdmin
FPDF Library
ADOdb
Perl
CPAN
PPM
mod_perl
Apache::ASP
In the directory \xampp\licenses you will find all licenses files of these programs and used libraries.