In my admittedly limited experience with Web-API, I can't see any way of finding out licence information via command-line.
From what I've seen, when you look at the commands available from core.help, it appears that web-API is mostly aimed at automating the really repetitive, mundane tasks such as:
- deploying agents to endpoints - this logic can then be used in scripts
- deleting endpoints out of the system tree - this logic can then be used in scripts
- changing extremely well-hidden configuration options, such as my personal favourite of enabling Drive Encryption system transfer functionality on your new ePO server
- locating an endpoint - this logic can then be used in scripts (I do this a lot)
- starting/stopping/listing/deleting scheduled tasks
- waking up agents
...etc. The list goes on and on.
Checking licence information doesn't seem to fall under the definition of repetitive, mundane tasks, despite the fact that a lot of organisations have many separate ePO servers which may need periodic true-ups (a la Microsoft true-ups/licence usage audits).