Irssi-mokuplam is a project mainly written in PHP, it's free.
A relaxed irssi IRC client theme with right-indented nicks
A theme for irssi 0.8.9+ with right-indented nicknames.
This theme truncates nicks at 9 characters, which might make it unusable in some networks/channels. If you know of a good way to set up network-independent indentation of nicks, please share!
Usage: copy to ~/.irssi, then /set theme mokuplam