Thank you for using HDP.
If you are talking about our support services – for support on this forum, we support any size cluster for free. For support beyond these forums we would need you to sign a support contract so we can provide you with a much higher level of support. Please let me know if you are interested in this. If so, we can refer you to our sales team.
If you are talking about how many nodes can be in an HDP cluster, then the answer is: HDP can be configured on thousands of nodes with no fee.
I hope that this answers your question.