Q:
Can i use CIS in my office, on publich computers, on multiply computers anywhere, etc.?
A:
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.