I don't know if this helps. But in the Javascript Open Source DayPilot version (daypilot-common.src.js), I added a resource at creation time like this:
I understand that the data object provided at creation time is a dictionary with key and values and it can be extended.
var event = new DayPilot.Event({
start: date_start,
end: date_end,
id: reservations[reservation].pk.toString(),
text: getStudioName(studioId) + ' ' + Dash + ' ' + reservations[reservation].fields.song,
backColor: getStudioBackColor(studioId),
cssClass : studioName.replace(" ", ""),
toolTip: made_by_id,
barColor: 'yellow',
resource: studioId,
song: reservations[reservation].fields.song,
});