My league membership is 130. When I go to the expansion tab in my league interface, slide runes over to ten and click, I get the following message "your league has reached it's maximum number of members"
Well, I found the answer. When I went to add another member with no space left, Plarium said do you want to add another member? I said yes and they said I had to donate 180,000 of each resource. Yep, no more runes, just my resources.