Is Centos legal?

I'm trying to figure out if centos is legal (or simply grey). Here's what makes me wonder:

1. They seem to go to great pains not to mention that they are based on redhat
2. in the FAQ they mention a policy about using the redhat trademark, but the link no longer exists.
3. When installing it it's not hard to find a lot of redhat code.

I don't bother much with the linux world anymore but I had a client that was wondering about it as his auditors picked up on it and wanted to know where his license was.

From serverfault Jim B

• In a word.. yes

  http://www.centos.org/modules/news/article.php?storyid=66

  in particular, the little snippit below directly from Redhat's legal team (bold by me):

  ---

  We understand that you are distributing, on your web site located at http://www.centos.org, CentOS Enterprise class Linux software that was developed using Red Hat's open source software. While Red Hat permits others to redistribute the software that constitutes Red Hat Linux, Red Hat does not authorize any person to use the RED HAT marks in association with such redistribution in any fashion, except by express agreement.

  ---

  So, basically, anyone has the right to redistribute the software (ie:linux) but cannot use the RedHat name/logo/etc with their distro. Which is why CentOS has removed the logos/name/etc.

  You can also find more info here: http://www.redhat.com/f/pdf/corp/trademark1.pdf which contains the section titled: "Guidelines For Marketing Software Products Containing Unmodified Red Hat® Linux® Software"

  3dinfluence : Exactly. Which is the reason you see CentOS refer to Red Hat as "a prominent North American Enterprise Linux vendor".

  Jim B : Thanks- what made me question it was all the redhat directories and such but from the link it looks like they didn't trademark the actual term redhat just the image and product.
  From Rex

• Not using Red Hat's trademark is part of what makes it so legal. Some Red Hat code is OK as long as it is GPL (or similar license). Other parts are proprietary and CentOS removes those parts.

  From kmarsh

• I don't know the specifics, and I'm certainly not a lawyer, but if certain code/applications/... that RedHat publishes are a derivative work of GPL code from GNU/Linux, they can't put the result under a license that doesn't allow copying. I believe, that would be illegal.

  It's a complex topic however.

  From Chris Lercher

• As an additional piece of information, Red Hat is generally supportive of CentOS (they're aware that many Centos installs are not lost sales of RHEL) and I believe actually puts some effort into keeping the difficulty level of stripping out the trademarked materials to a minimum.

  From Ophidian