The “host” for a system is the individual or entity that owns or controls the site where the system will be installed.  In the case you present, the host is a different individual or company from the owner of the system (the individual or company that will have title to the RECs produced by the system).

Systems for which the owner and the host are different individuals or companies are eligible for participation in the DG RFP.  However, such systems are typically required to submit additional documentation in the form of a “Host Acknowledgment”.  A Host Acknowledgment is a statement from the host that the host knows about the planned system and agrees to the system being installed.  A sample of the Host Acknowledgment from a prior procurement event is provided here:

https://www.ipa-energyrfp.com/2016-renewable-energy-resources-section/

(click on Appendix 5 under Spring 2016 Distributed Generation FINAL RFP Documents).