What Furling is asking for can only be done as a client mod. Parse NewChatHud_AddLine(%message) for kill messages and add an RTB popup by calling whatever the function is.
Or just use
function clientCmdServerMessage(%tag,%msg,%a1,%a2,%a3,%a4,%a5,%a6,%a7,%a8,%a9,%a10)
{
%detagged = detag(%tag);
%det = detag(%msg);
if(%detagged $= "MsgYourDeath" || %detagged $= "MsgClientKilled")
and go on from there
the rtb popup function is this, which you can find the correct arguments for throughout System_ReturnToBlockland/modules/client/connectClient.cs
RTBCC_NotificationManager.push();
And you can also check to see if the client has RTB and if not, execute a support .cs file in the add-on archive which creates a temporary notification manager
Here are a few instances of the ::push method
RTBCC_NotificationManager.push(%user.name,"has invited you to play.","house",%from@"_invite",-1);
RTBCC_NotificationManager.push("Disconnected","You have been kicked.","delete");
RTBCC_NotificationManager.push(%user.name,"has just started a server.","world",%user.id);
RTBCC_NotificationManager.push(%user.name,"has just signed in.","user",%user.id);
RTBCC_NotificationManager.push(%person, %talk,"comment_add",%this.user.id@"_msg",-1);
