How to protect a commercial web system from cloning and organize license control?

Question

CMS

There is a commercial web-system that has a demo mode and a working mode. The demo differs from the working one in the presence of restrictions and the absence of a key that removes restrictions. It is assumed that users freely download the demo mode and, if desired, buy a key and install it themselves.
How to organize reliable technical protection of a web resource from unlicensed copying and use with an existing commercial key?
How to technically organize the accounting of licenses in your database, for example, and make it possible to record newly installed demo copies?
Those. A person can buy a key and start cloning a working system.
Please share the practices of protection, storage and control of license keys, ways to disable an unauthorized resource. Thank you.

Answer 1

SaaS.

Answer 2

but no way. you can, of course, encrypt with an ioncube, but who really needs to decrypt
the best option to make an API, where users will log in and work with the system via api
, and give the users themselves only the front and that's it

Answer 3

Any code that gets on the computer of an experienced and cunning programmer will be cracked, a matter of time.
The only solution is not to give this code, as Mikhail Osher correctly noted - a SaaS solution.
PS About 5 years ago, in one large online store, CMS Bitrix was used for a corporate portal. Used by about 2000 people. Used a broken version.