Apparently they raised $100M[2] back in 2012.
They have since agreed to distribute these domains through 19 registrars[3] (eNom, Name.com etc)...
Looking at their ICANN PIC submission[4] they have registered no fewer than 200-250 LLCs
[0] : https://gtldresult.icann.org/application-result/applications...
[1] : http://icannwiki.com/index.php/Donuts
[2] : http://money.cnn.com/2012/06/05/technology/donuts-domains-fu...
[3] : http://www.donuts.co/news/donuts-adds-another-seven-generic-...
[4] : https://gtldresult.icann.org/application-result/applications...