Can i use CIS in my office, on publich computers, on multiply computers anywhere, etc.?
The short answer is: Yes. You may consider buying PRO version for extra features (such as encrypting the sent/received plain texts or getting 24/7 technical help - which includes pc tune-up, installing&setting up CIS on your computer(s), troubleshooting your pc-related problems, etc.), but the simple Comodo Internet Security is free.
You may need to check out the license part regarding country policies.
Another short answer: yes it is. If you want to secure a larger network, you may want to look into Endpoint Security Manager https://forums.comodo.com/comodo-endpoint-security-manager-b115.0/
It offers the same CIS protection, but with added centralized administration and additional features. (Not a free product, but you can try 5 endpoints free.)
Thanks for using and recommending Comodo Internet Security.