How to get a steady ,or commercial license key for NVENC SDK

Currently,I use the “NV_CLIENT_KEY_TEST” key(for v3.0 sdk),or “NV_ENC_CLIENT_FREE_TRIAL”(for v2.0 sdk),but they

are seems not a steady one,so how can I get a steady,or just commercial license key for NVENC SDK? Should I be a

NDA member?