If you are connecting to your co-worker's or friend's machine and using the target machine's IP address all you need is the NoMachine Player which comes with all NoMachine software. It is the person responsible for the target machine which must make sure that the software installed has been activated with the appropriate software license.  You do not need a software subscription to connect to someone else's computer over IP.

You can also use the free Enterprise Client or the NoMachine mobile applications to connect, these are free to install and use.

https://download.nomachine.com/enterprise/?product=enterprise-client
https://download.nomachine.com/mobile/

Instead, if you want to connect to the target machine using the NoMachine Network service, so using its Machine Id, you will need to acquire a NoMachine Network subscription.