The "protection" you speak of is that consumers can associate a producer with a product. In this case the producer of the original product was Sun which is now part of Oracle. Thus someone who gets an update for "Open Office" is getting it from the one true source for Open Office.
The freedoms provided by the Open-Source license allow someone to fork that code to create a "new improved product" - but that product can't be called "Open Office". In this way consumers can't think they're getting x and end up with y.
If the consumers are concerned about Open Office, then it's their choice to go to Libre Office. They are in effect opting-in to a change. Changes of this nature have to be opt-in, there's no way around that.
Allowing multiple people to use a trademark, or worse encouraging court battles over who is the "one true heir" to a trademark would not be in the consumers interest.
Clearly a fork can not have any claim on a product name because if it did there exists the possibility for infinite forks, and infinite products with the same name. This in no way serves the consumer, and specifically it does not facilitate the identification of the product, not does it serve to identify quality or other characteristics.
In some countries, when trademarks are transferred, there must be a continuity in the underlying product or the trademark is lost. (You cannot just buy a famous trademark and ship something completely different with a sticker placed on it.)
Anyway, as you stated in the last paragraph, there may be an infinite number of forks, and that is the core of the problem with trademarks and open source. At the moment of forking, the source codes is identical. Then they start to differ. Which one is truer to the original one? Software is not a shoe. I see the continuity of a software project in the philosophy behind it.
Who is the true producer (the one that guarantees the "quality" for the consumer) in this case? The organization or the community? Which part of the community?
In my opinion, this is a big problem that needs to be solved in the future. Maybe using a trademark are not a good idea for an open source project...
"In some countries, when trademarks are transferred, there must be a continuity in the underlying product or the trademark is lost."
If you say so, but it's certainly not the case in the US, or most other countries. Ford for example regularly resurrects names like Mustang, or GT40, and there is seldom any continuity in the underlying product. BMW bought Mini from British Leyland, and developed a completely new car, which pays homage to the Mini shape, but there is no continuity between the two products.
In software there are endless accounts of "complete rewrites" which ship under the same name as an earlier product.
I think trademarks work perfectly well in the Open Source space. The project originator (usually) owns the trademark - others are free to get their own name. In this case it's pretty cut & dried. Oracle owns the product Open Office. Anyone can fork it, but the one true "Open Office" is the one from Oracle.
Now you may argue the merits of the fork surpassing the leader, and if customers buy into the argument they can "opt in" to the new fork. That's their choice. I don't think this hurts consumers, and I don't think it hurts Open Source.
"In some countries, when trademarks are transferred, there must be a continuity in the underlying product or the trademark is lost. (You cannot just buy a famous trademark and ship something completely different with a sticker placed on it.)"
[Citation needed]
In some ways you're technically correct I guess, but you're phrasing it in a way that leads to depictions of reality that are widely inaccurate. The thing is that you can't apply trademarks from one business domain to another willy nilly; but this has nothing to do with the transfer of them. (e.g. if I sell apples under the brand name 'chiquita', that may be a problem, trademark-wise; but selling tv's under the name 'chiquita' may not be). This has nothing to do with the transfer of the trademark.
Then again, I don't claim to know anything more than the generalities of trademarks in just a few countries, so I'm interested in examples of your points from specific legal systems.
The freedoms provided by the Open-Source license allow someone to fork that code to create a "new improved product" - but that product can't be called "Open Office". In this way consumers can't think they're getting x and end up with y.
If the consumers are concerned about Open Office, then it's their choice to go to Libre Office. They are in effect opting-in to a change. Changes of this nature have to be opt-in, there's no way around that.
Allowing multiple people to use a trademark, or worse encouraging court battles over who is the "one true heir" to a trademark would not be in the consumers interest.
Clearly a fork can not have any claim on a product name because if it did there exists the possibility for infinite forks, and infinite products with the same name. This in no way serves the consumer, and specifically it does not facilitate the identification of the product, not does it serve to identify quality or other characteristics.