"Bot Signatures: Class of signatures that identify legitimate or malicious web robots by looking for specific patterns in the headers of incoming HTTP requests. With the release of BIG-IP 14.1.0, this feature requires a separate license. Bot signature updates are part of the Threat Campaigns subscription-based service license. Without a Threat Campaigns license, bot signatures cannot be updated using manual or automatic updates; however, you can still add custom bot signatures.
Note: Bot signatures are updated on each major version; however, BIG-IP 14.1.0 includes updated bot signatures (the bot signature dated with the time of the release is part of the BIG-IP 14.1.0 ISO package.) In versions prior to BIG-IP ASM 14.1.0, the previous four update files are packaged in a single file.
Note: Beginning in BIG-IP 18.104.22.168 the Live Updates Available notification will not appear for Bot Signatures if that feature is unlicensed."
In other words, you will get bot signature updates either over a TC subscription or with every major release.