Is there a way to find out if a site is using CI as framework?

[eluser]phoenixg[/eluser]
[quote author="skunkbad" date="1340028691"]Starting with CI v3, I believe part of the new license requires that a site basically reveal that it is using CI, but that doesn't help you for versions less than 3. Actually, the likelihood that less than 1% of people will understand that license means you don't really have any guarantees. It might be another way to detect CI usage.

Then, there's another way, but not always reliable. If you try to access one of the files in the system or application directory, you would get the message: "No direct script access allowed", but if somebody is using .htaccess to block access, the message would not be seen. In that case, the generated 403 error may be an indication that the site is using CI, but CI is probably not the only one with a system and application directory.[/quote]

Thank you, very detail and professional explanation.