This works on OS X Server on Mountain Lion.
Ok... i did some digging around... and struck gold.
The digging part is not for the "faint of heart" since the Terminal is your best friend and some coding knowledge is involved. Suffice to say my trip in Wiki Server 4 land led me through Ruby on Rails code. I was surprised to find that i'm able to read ruby code, and i don't know Ruby at all. After looking through Model Views and Controllers i figured out the solution was simpler than i anticipated.
To modify the title on the first page you need to edit a .strings file. You need to use the download version (not the mac app store app) of TextWrangler or some other editor that allows Authenticated Saves (save files as other users). Make sure the Wiki service is off... the slider in the server app is off.
The location of the file depends on your language locale that you use:
/Applications/Server.app/Contents/ServerRoot/usr/share/collabd/coreclient/locales/en.lproj
where "en" can be either de, es, fr, it, ja, ko, nl, zh_CN, zh_TW depending on your wiki language.
First()
you need to right click on the file and "Get Info" and adjust the permissions temporarily for "Everyone" to "Read and Write".
Open the file in TextWrangler and find the key general.os_x_server and under it you can modify the string "OS X Server" to anything you want "My own company Wiki".
Save()
the file.
Second()
you need to right click on the file and "Get Info" and adjust the permissions temporarily for "Everyone" back to just "Read".
Move()
the slider in the Server App to On again for the wiki.
Enjoy!!!
