H2O is an Open Source, Distributed, Fast & Scalable Machine Learning Platform: Deep Learning, Gradient Boosting (GBM) & XGBoost, Random Forest, Generalized Linear Modeling (GLM with Elastic Net), K-Means, PCA, Generalized Additive Models (GAM), RuleFit, Support Vector Machine (SVM), Stacked Ensembles, Automatic Machine Learning (AutoML), etc.
If AutoML will be extra JAR of part of H2O, it all cases it should be handled as core extension.
The AutoML Rest API should depend on the AutoML core extension.
Example code for this can be XGBoostExtension and RestApiExtension