Derivatives

Apache-SSL
Apache with Secure Sockets Layer (SSL) built-in, not as a module.
http://www.apache-ssl.org/

IBM HTTP Server
Features support for SSL V2 and V3, Fast Response Cache Accelerator (Windows NT only) and native platform install.
http://www-4.ibm.com/software/webservers/httpservers/

Oracle HTTP Server Powered by Apache
Apache adapted to work with Oracle's Internet Application Server.
http://www.oracle.com/ip/deploy/ias/index.html?web.html

Stronghold Enterprise Apache
Apache redesigned with rigid security features.
http://www.redhat.com/software/stronghold/

StWeb Stratos Web Application Server
Apache rewritten to serve pages written in the Stratos programming language.
http://www.stweb.org/

WebTen
Apache-based web server for MacOS Classic (9.x and below).
http://www.tenon.com/products/webten/