Although VPN usage is not strictly disallowed, you should consider the risks of using a VPN with Honeygain.
Most of the servers used by VPN providers give you a Data Center type (DCH) IP address, which is not allowed by Honeygain and would cause your account to be suspended. Moreover, if other users happen to use a VPN with Honeygain on the same IP address, your account will get suspended too, as the IP address in question would be registered for all the accounts that use it.
All in all, by using a VPN you are taking the risk of getting your account suspended, especially if the end-point IP address usage type is DCH, hence, we do not recommend using a VPN with Honeygain.