ZyWall USG 100 PLUS - SecuExtender License for Windows Client

Hi everyone,

I have a Zyxel USG 100 PLUS and I need to connect multiple users to the SSL VPN.

The free firewall limit is 2 tunnels at a time.

I would like to connect 2 other users for distance work (for a total of 4 users)

We have "Windows 7" and "Windows 10" computers.

Do I have to buy a license?

If yes where?

Which?

Thank you!