You don't need any license for netflow:
Cisco IOS XE Software Feature License Types
Cisco IOS XE Software also offers you a granular licensing schema. You can select individual feature licenses based on your specific feature support requirements. Specific feature licenses are provided in right-to-use (RTU), number-of-sessions (NOS), or both formats, depending on the type of feature being licensed. An NOS license is for the maximum number of simultaneous sessions that are allowed on the Cisco ASR 1000 Series platform. At FCS the following features are licensed separately: IP Security (IPsec) encryption, Firewall, Flexible Packet Inspection (including Network-Based Application Recognition [NBAR] and Flexible Packet Matching), Broadband Aggregation, and Cisco Unified Border Element (SP Edition) (also known as Session Border Controller [SBC]). Licenses are not required for Network Address Translation (NAT), NetFlow, generic routing encapsulation (GRE), or basic routing services.
http://www.cisco.com/en/US/prod/collateral/routers/ps9343/product_bulletin_c25-448292.html
HTH
