Netbackup Licensing Guide

I can see you a partner and shall send you a private message with pricing guide and it will also discuss the difference between traditional(agent as you said) and capacity based license.

Platform Base Licensing Summary
NetBackup Platform Base licensing is a capacity-based model using the amount of source data protected per-terabyte as the sole or primary calculation meter. This model is commonly referred to as capacity licensing or Front-End Terabyte (FETB) licensing. The Platform Base model enables customers to license NetBackup based on how much source data is protected rather than the number of NetBackup clients, agents, servers, and options deployed as with Traditional licensing.

Traditional Licensing Summary
The Traditional (or “server”) licensing model is based on the number of NetBackup clients, agents, servers, and options that NetBackup will be protecting or run on. A customer purchases the same number of licenses as the count of clients, agents, servers, and options. As they deploy additional NetBackup clients or servers or attach additional tape drives or storage to NetBackup, additional licenses for appropriate NetBackup products are required.
If a server is protected by multiple Master Servers, a license is required for each Master Server Domain.