Yes. Google Play Services is required for all of our Android integrations. The Google Play Services Library required is the ads identifier library (com.google.android.gms:play-services-ads-identifier), and integrating this library alone would be enough.
If you do not integrate Google Play Services SDK, we will still serve interstitials but we will not be able to serve rewarded video. Our rewarded video format requires that our SDK be able to access a device's ID. Additionally, our SDK will not be able to use an ID for advertiser install tracking purposes, which means that in some situations monetization might be hurt and/or fill might be affected if the advertiser requires device IDs for install attribution.