I think you'd just have to change this file:
$ diff wiki/languages/Messages.php wiki/languages/Messages.php.orig
< 'loginreqlink' => 'log in',
'loginreqlink' => 'login',
"login" should only be used as a noun or adjective ("the login form", "a user's
login"). "log in" is the preferred form for verbs ("you must log in to edit this
From the MS Manual of Style (and many other style guides, I'm sure!):
log on to, log off from, logon (adj)
Use log on to to refer to connecting to a network and log off from (or simply
log off) to refer to disconnecting from a network. Do not use log in, login, log
onto, log off of, logout, sign off, or sign on. An exception is when other terms
are dictated by the interface.
Use logon only as an adjective, as in "logon password," not as a noun.
You are prompted for your password while logging on.
Reconnect when you log on to the network.
Some networks support this logon feature.
Remember to log off from the network.