UnrealIRCd
... that UnrealIRCd is used on the largest number of IRC servers?
... that <b id="mwFRI"><a href="./UnrealIRCd" id="mwFRM" rel="mw:WikiLink" title="UnrealIRCd">UnrealIRCd</a></b> is used on the largest number of <a class="mw-redirect" href="./Internet_Relay_Chat" id="mwFRQ" rel="mw:WikiLink" title="Internet Relay Chat">IRC</a> servers?