Writing an open source clone of commercial software - colloquial naming?

Question

Suppose there is a very expensive commercial software program. For example, we'll call it Zyzzy's Super Expensive Software. Assume the Zyzzy Software Corporation has a trademark on its logo, but no explicit trademark on Zyzzy's Super Expensive Software as a product name. Zyzzy Software's primary product, responsible for a majority of their business, is Zyzzy's Super Expensive Software - if that program were to go away, the company would dissolve with it.

The company itself occasionally abbreviates the program as "ZSES", but colloquially in the industry the program is used within, it's simply referred to as "Zyz" or "Z", e.g. "Use Zyz to do that" or "I just updated to the latest version of Z today." Assume also that the company never uses the terms "Zyz" or "Z" in "official" communications or documentation, but perhaps its Twitter account has whimsically acknowledged the colloquial term, for example: "Hey Zyz-a-maniacs!"

Suppose I want to write an open source version of ZSES. I'd be doing this entirely "clean" - i.e. by simply observing the behavior of ZSES and implementing it my own way. No access to code, reverse engineering, etc. - purely based on freely available public documentation and observing the behavior of the commercial product. The actual output of ZSES and my clone are not necessarily guaranteed to be exact and in fact likely won't be, but would be functionally equivalent such that my clone would be a very simple replacement for almost all use cases. I would use a unique UI, but functionally the program could perform the same functions, and also let's assume my UI might be improved over the original product. In other words, my clone could potentially have a significant impact on Zyzzy's Software Company's sales and bottom line.

Now assume I want to decide what to name my clone. Similar to classic examples like LibreOffice (arguably based on Microsoft Office) and even Linux (Linus + Unix?), I decide I want to name my program "LibreZ" or "FreeZyz".

Given that "zyz" is just a colloquial name, not officially used by the company itself and definitely not trademarked but instantly recognizable by anyone in the industry, am I putting myself at obvious risk of litigation, assuming the situation that Zyzzy Software realizes they're losing money and I'm the reason? Consider that anyone in the industry would immediately see "FreeZyz" and know that it must be a free version of ZSES.

If Zyzzy had trademarked the colloquial names, then this would likely be a simple case and could easily be argued to potentially cause confusion. But the key point in my scenario is that the company has not trademarked the colloquial names, but perhaps it might be assumed by a lay person that they are trademarked because they are so closely associated with the product.

Naturally I know the easy answer is "you can be sued for anything" but I'm thinking beyond that - would a company have a credible case against a developer doing this? Could a company use a "prior art" type of argument to retroactively register a trademark and then go after a developer in this scenario, since it could be very easily demonstrated that the colloquial term is strongly associated with the commercial product?

(Note: When I originally wrote this I had used "John" and "Johnson" for the software and company name, but I decided to change it to "Zyz" because "FreeJohn" could be argued to just contain a common name, but "Zyz" is unique enough that it'd be easy to understand how it might be uniquely associated with a specific industry. It's also not a "generic" term, as in, perhaps you might colloquially refer to an iPad as a "pad" but "pad" is a generic enough term; "Zyz" is definitely not generic despite not being trademarked.)

Answer 1

What is and what is not a protected trademark depends on the law of the country, and varies by country. In some countries, of which I understand the UK is one, no mark is protected unless it is officially registered. In other countries, of which I know the US is one, use of a mark to identify a product or service that is being sold or advertised commercially (that is, use "in trade") is enough to obtain a degree of protection.

So the statemetn in the questiuonb that:

If Zyzzy had trademarked the colloquial names, then this would likely be a simple case and could easily be argued to potentially cause confusion. But the key point in my scenario is that the company has not trademarked the colloquial names, but perhaps it might be assumed by a lay person that they are trademarked because they are so closely associated with the product.

is not quite correct. If this is in the US or a country with similar tr4ademark laws, then the lack of official registration does not end the matter. The question is not whether people think the mark is a trademark, but whether people associate it with the product (here ZSES). If they do, then at least a degree of protection is obtained in such a country.

But that only starts the inquiry. A mark is only infringing if it is an exact copy of a protected mark, or if it is sufficiently similar that it may reasonably be expected to cause confusion, leading some people to believe that the product marked or advertised with the allegedly infringing mark is in fact the protected product, or comes from the same source (say the same software firm) as the protected product. It can also be infringement if people are reasonably confused into falsely thinking that the infringing product has been sponsored, approved, or endorsed by the makers of the protected product. It can also be infringement if there is a deliberate attempt to create either kind of confusion.

But when there is no such confusion, a reference to an actual trademark is usually not infringement. Comparative use ("This software is 10% faster than ZSES") or statements of compatibility ("This software will load parameter files mproducews by ZSES 5.3") are both forms of nominative use and ar not infringing. In general, when one uses a mark as the name of a product, that is nominative use, and is not infringing, provided that it is clear to a reasonable person that the profuct is not the protected product, nor endorsed or approved by the makers of the protected product. A dislcailer can help in making this cleart. For example

The marks "ZSES" and "Zyzzy" are trademarks of the Zyzzy Software Corporation (ZSC). These marks are used here to identify and refer to products created by ZSC. The FreeZ software suite is not a product of ZSC, and has not been endorsed or approved by ZSC.

Thus a mark which refers to an existing mark, but is clearly different, is usually not an infringing mar. For example, neither "OpenOffie" nor "LivreOffice" has been held to infringe on "Microsoft Office". (Note that just "office" is too generic to be protected.) If someone created a smartphone with the brand name "Pear" that would be an obvious reference to Apple, but probably not a trademark infringement.

So "FreeZyz" or "FreeZ" would probably not be held to be infringements, even if "zyz" had been registered as a trademark.

Note however that "widely-known" (aka "famous") marks get additional protection under US law.

Note also that trademark law can be complex and technical. It also varies significantly by country, and a product trademarked in one country may have no protection in a different country. Before spending significant effort and money marketing a new product in such situation, one would be wise to consult a lawyer with significant trademark experiences and expertise min the relevant country. It might be wiser to choose a name with no relationship to the name of the product being imitated.