Hello!
Well, when LoL was taking over the Moba-scene with their "free to play" S2 realized that they was growing way much slower. Sadly.
So S2 also made Heroes of Newerth F2P as well.
The only difference in the beginning was that a purchased account had a different namecolor.
That have changed a bit today. When you buy an account today it's called a "verified account". That means that you have everything unlocked, and you can modify your gaming/queue-options.
Being unverified in HoN is probably the worst gamingexperience ever for a noob. You are being teamed up with other useless players and shitty smurfs that wants to feel a bit better cause they are too bad for their own rating.
Unverified forces you to only play "All pick"-mode, which still is the most popular gamemode. You cannot play verified games with verified players.
The difference is not that big anyways, 1500-1650 unverified and 1500-1650 verified is about the same, horrible ragekids all over.
When playing HoN you gain experience, when you hit level 3(or 5?) your account will automatically be verified.
Best of luck,
AlphaTim