This isn't clear to me at all:

"A person that creates units of this convertible virtual currency and uses it to purchase real or virtual goods and services is a user of the convertible virtual currency and not subject to regulation as a money transmitter. By contrast, a person that creates units of convertible virtual currency and sells those units to another person for real currency or its equivalent is engaged in transmission to another location and is a money transmitter.
In addition, a person is an exchanger and a money transmitter if the person accepts such de-centralized convertible virtual currency from one person and transmits it to another person as part of the acceptance and transfer of currency, funds, or other value that substitutes for currency."

My interpretation:

Our business (an ad network) accepts Bitcoin from users (advertisers) and pays users (publishers) in Bitcoin. From the sounds of this we are a money transmitter and an exchanger because:

1) we accept such de-centralized convertible virtual currency from one person (advertisers)
2) as part of the acceptance and transfer of currency (currency and or virtual currency?) (i.e. paying publishers for displaying ads), ..., or other value that substitutes for currency (i.e. virtual currency?)

It's ambiguous. We are not located in the US also. I will speak with a lawyer....