I'm developing a small open-source plugin for a fairly well known CMS, which as far as I can tell has a trademark on the product and company name. It's starting to get a bit of traction, so I'm in the middle of setting up a website to host the documentation and getting started guides.

It's fairly common to see open-source projects use the name of a brand or company because it makes finding them a lot easier, but are there any legal requirements on the maintainers to declare that they're not affiliated with the company, or something like a copyright notice? Would I need to ask the company for permissions to use their name in an open-source project?

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Using a trademark to refer to that brand itself is generally fine. Using a trademark as part of your name is not. Your project shouldn't mislead users in thinking that your plugin would belong to or be part of the real brand, or would otherwise be official.

For example, this would be fine and your name can't be confused with the trademark:

Flooblargh – a 3rd party plugin for TrademarkCMS

Whereas a name like Trademark-Flooblargh wouldn't be fine: that would look like it would be part of that brand, and would therefore mislead users.

  • A lot of rot crept in with the UNIX trademark. Very often if you acquired a license to UNIX, you had to agree to acknowledge ownership of the UNIX trademark whenever you referenced it: "UNIX is a trademark of X/Open" or whatever. A lot of people started to assume that all references to trademarks needed to be acknowledged in this way: "IBM is a trademark of IBM". That's not the case. Using a trademark to refer to the product or company that owns the trademark is perfectly OK and does not require any permission, license, or acknowledgement. IANAL. Sep 20, 2021 at 13:47

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