This was the statement that caused cubecraft to remove voting rewards in August. The old voting rewards were 1 cubelets and 300 experience which could also be a daily gift or such for donators... but wait a second...If you give anything in return for voting for your server, such as “Vote tokens” or other items, the same restrictions apply as for hard currency.
This means that the old voting rewards were completely fine as it follows the same restrictions as for real money (hard currency) by being purely cosmetic. Experience gets you more glass colors and stuff and we all know what cubelets do. This means the old voting system could easily be brought back without cubecraft havingn any fear of being blacklisted....the same restrictions apply as for hard currency.
Let's talk about what vote tokens were and why I believe voting to get in game advantages was removed. I like going onto various random servers other than cubecraft every now and then and I found a server that have out vote tokens. These vote tokens could give you donator ranks if you had 500-2000 of them (1 token per vote) so they used this to justify having their donator ranks have in game advantages (even though it is against the EULA to sell in game advantages regardless of whether or not regular players can get them.) This method probably annoyed mojang and to clear up confusion about having vote tokens as an easy way to avoid the Eula they released the statement above.
No real part of the minecraft EULA is specifically about voting but this may apply.
let other people get access to anything we've made in a way that is unfair or unreasonable;
Minecaft EULA
spigot thread on the topic