I see many threads and two resolved bugzillas on this topic, but none referring to 5.0 -- most recent is September 2007.
I have changed both LogoURL in jetty/webapps/zimbra/skins/_base/{base,base2}/skin.properties and splashScreenCompanyURL in jetty/webapps/zimbra/WEB-INF/classes/messages/*
but the logo on the login page still links to
http://www.zimbra.com/
Where else can I look?
Even hard-coding the URL in ZimSkin.
js (replacing @LogoURL@ with my URL) doesn't work.
I have made no other changes to the skins. Rather than pointing at new logos, we simply overwrite AppBanner.png and LoginBanner.png with our own. That part is working.