We love it when people use or extend Zeek for either non-profit or commercial purposes. Zeek’s code is open-source under a very permissive BSD-style license, which means you’re free to use it in almost any way you like.

We emphasize however that we retain all rights to the Zeek name and logo, as well as the Bro name and logo and related terms and catch phrases; collectively referred to as the "Zeek marks" in the following. This includes using the marks for promoting websites, services, businesses, and products. While generally we’re fine giving people permission to use the marks under many circumstances, we reserve the right to decide on a case-by-case basis. Our main objective here concerns avoiding confusion: We want to ensure that when people talk about "Zeek" or "Bro", they all mean the same.

In the following we collect a few guidelines for usage that’s ok, and some that’s not. If in doubt, please ask us and we’ll be happy to discuss your situation; most likely, we’ll be able to work something out.

Generally, it’s fine to use the Zeek or Bro name without specific permission if all of the following apply:

• You use "Zeek" or "Bro" only to refer to the official Zeek/Bro distribution as available on zeek.org, not any derived or modified version.
• You make clear that you are not part of the Zeek Project or otherwise representing it. A simple disclaimer will take care of this if there’s any risk of confusion.
• You are a non-profit entity with no financial interest in any products or services that would benefit from the use of the "Zeek" or "Bro" name.
• You are not using the Zeek or Bro logo.

If you would like to use the Zeek marks in any other way, including displaying the Zeek or Bro logo, please contact us. We generally don’t have objections to people using the marks for their web sites or businesses, but we would like a chance to review it. Generally, we’ll quickly approve your use if you agree that our rights to the marks are valid and superior to yours, and you take appropriate steps to make sure people don’t confuse your website, code, or product for ours. Usually a short email conversation should clear everything up in short order.

The one problematic case we would like to point out here explicitly concerns code changes: if you modify or extend the code distributed on zeek.org, you can’t call it "Zeek" or "Bro" anymore. This restriction is necessary to ensure that Zeek users understand what the Zeek Project has signed off on, without risking ambiguity that would undermine the trust into the system. In short, if it’s called "Zeek" or "Bro", it must be our Zeek/Bro. If you’re unsure if this applies to your setting, please get in touch with us. We expect that most cases can be resolved quickly. For example, if you clone our repository on GitHub to work on some patches, just refer to that version as your "patched Zeek" and you’ll be fine.

We reserve the right to update our trademark policy at any time, effective immediately.

(Parts of this document have been inspired by the Software Freedom Law Center’s Legal Issues Primer for Open Source and Free Software Projects.)