This is a rough example of integrated mediawiki authentication
originally written to work on a customized MW (some tables are different from standard)
so to adapt this to your case you'll most likely need to tweak this 

Also keep in mind that probably a better solution would be to create a single signon site.

Author: evgeny.fadeev@gmail.com (Evgeny)

==Minimal directions==

1) Add the following to your settings_local.py (with relevant modifications):

USE_EXTERNAL_LEGACY_LOGIN = True            #enable external legacy login
EXTERNAL_LEGACY_LOGIN_AUTHENTICATION_BACKEND = 'mediawiki.auth.IncludeVirtualAuthenticationBackend'
EXTERNAL_LEGACY_LOGIN_AUTHENTICATION_MIDDLEWARE = 'mediawiki.middleware.IncludeVirtualAuthenticationMiddleware'
EXTERNAL_LEGACY_LOGIN_MODULE = 'mediawiki'   #current module
EXTERNAL_LEGACY_LOGIN_HOST = 'yoursite.org'  #wiki domain
EXTERNAL_LEGACY_LOGIN_PORT = 80              #port, probably 80
EXTERNAL_LEGACY_LOGIN_PROVIDER_NAME = 'My Wiki' #html allowed
MEDIAWIKI_URL="http://yoursite.org/wiki/index.php"
MEDIAWIKI_SALT_PASSWORD=True #or False - depending on your LocalSettings.php
MEDIAWIKI_INDEX_PHP_URL='/wiki/index.php'
MEDIAWIKI_COOKIE_DOMAIN='.yoursite.org'  #for cross subdomain login
MEDIAWIKI_SESSION_COOKIE_NAME = '' # probably '<dbname>_<dbtblprefix>_session'
MEDIAWIKI_PHP_SESSION_PREFIX='sess_'  #depends on your setup
MEDIAWIKI_PHP_SESSION_PATH='/var/lib/php/session'
SESSION_COOKIE_DOMAIN = '.yoursite.org' #use this notation for cross-subdomain login

2) Configure apache to access forum "backend" via the wiki domain.
Example configuration is in the end of the doc.

3) Install two wiki extensions WsgiInjectableSpecialPage, UserRegister -
the usual MW way. You might want to disable traditional wiki registration.

4) grep files for 'yourwiki' and change that to your own taste - there are some
hardcoded urls

5) Templates are in templates/mediawiki - you probably will want to customize them,
form js media: templates/content/js/mediawiki-login.js
form css media: templates/content/style/mediawiki-login.css

==Requirements==
wiki and forum must live in the same mysql database for registration to work,
however login will work even if this is not the case

you must own both wiki and forum or there must be good trust relationship 
between the owners - because password is shared

==Notes on how external login currently works.==
password and login are entered in the login form.
these are checked against mw api

password is saved in the auth_user table (the django way)
so if you at some point set USE_EXTERNAL_LEGACY_LOGIN = False
wiki passwords and logins will still work on the forum

login action is partially synchronized btw wiki and forum (from forum to wiki,
but not the opposite way yet)

when users first register - either on wiki or forum they are logged in on both

on registration they receive a greeting email - you will want to customize messages

technically, on the wiki registration form is injected via apache SSI
- using include virtual call

there is a possibility for cross-site scripting attack if wiki session is stolen

==Apache setup example for the wiki==
This assumes that wiki and forum facing the user are on different subdomains.
Also this setup is just an example - you may do better :).
Forum setup in apache is described in main osqa INSTALL document - that's extra.

<VirtualHost your.ip:port>
     ServerAdmin admin@yourwiki.org
     DocumentRoot /path/to/wiki/root #dir containing wiki directory
     ServerName yourwiki.org
     AddOutputFilter INCLUDES .php
     Alias /backend/content/ /path/to/forum/templates/content/
     AliasMatch (content\/style\/[^/]*\.css) /path/to/forum/templates/$1
     AliasMatch (content\/.*) /path/to/forum/templates/$1
     <Directory /path/to/forum/templates/content>
          Order deny,allow
          Allow from all
     </Directory>
     WSGIDaemonProcess my-forum-wiki-side  #use daemon mode so to avoid potential timezone messups
     WSGIProcessGroup my-forum-wiki-side
     WSGIScriptAlias /backend /path/to/forum/cnprog.wsgi
     CustomLog /var/log/httpd/yourwiki/access_log common
     ErrorLog /var/log/httpd/yourwiki/error_log
     LogLevel debug
     DirectoryIndex index.php index.html
</VirtualHost>
<Directory /path/to/wiki/root>
        Options Includes
        <IfModule sapi_apache2.c>
                php_admin_flag engine on
                php_admin_flag safe_mode off
        </IfModule>
        <IfModule mod_php5.c>
                php_admin_flag engine on
                php_admin_flag safe_mode off
                php_admin_value open_basedir "/path/to/wiki/root:.:/tmp" #tmp used for sessions
        </IfModule>
</Directory>