Line 50 of that file would be:
$ubbt_lang['IRC_COPY'] = "<a href=\"https://ubbdev.com/forums/ubbthreads.php/ubb/showflat/Number/310947/an/0/page/1\">pJIRC UBB Addon " . $ubbt_lang['IRC_VERSION'] . " by Gizmo.</a>"; // The support URL at UBBDev.
I don't see a syntax error in the above; you could try making sure that yours matches it, or remove the text between the ""'s completely.
Another option would be the naked shoutbox as mentioned, this script is for those who'd prefer relying on a 3rd party irc server.