Indeed, Linux is probably the most famous. It's trademarked because someone else tried to trademark "Linux" and then shake down vendors for 10%. It went to court, the trademark troll lost and the trademark itself was assigned to Torvalds.
It's now administered by the Linux Mark Institute.
The AT&T Unix is probably "the" Unix, if there is one, but the name got sold eventually to The Open Group which licenses it to compliant systems.
So it's now a bit more like x86 (family of similar products that work somewhat similarly, though x86 doesn't need a license any more) rather than Pentium (a product or range from a specific company).
its website was kurento .org but the trademark of the name (and the domain) is owned by Twilio, who recently had the gesture of redirecting all accesses from this domain to their own, without prior warning. No replies to emails, or reasons stated. Not that they needed one though, as they are indeed the owners and can do whatever they want. Just a nice "contribution" they made to OSS, it seems.
Wouldn't be surprised if that wasn't a "let's send all the random domains we have lying around to the main site" bulk change and whoever did it didn't realise and if anybody's reading the emails they have no idea where to start finding out who that was.
I mean, that's not exactly great either if true, but I think it's just as much a possibility as this being intentional.
I would have hoped that in such a case, talking it over email and/or phone if needed would be a way to restore the domains that were actually in use. But apparently, emails were sent and never responded. In any case we took the chance to move it all so now it's a solved problem. The manners weren't great, tho.
Right, the only thing I'm arguing here is that it's plausible that every step, including the lack of a reply to the emails, could easily have been down to "the organisation was insufficiently organised."
Note that I've had to run around helping projects deal with both that sort of situation and the sort where the company was deliberately screwing over the project out of active malice (take a bow, Nagios Enterprises) and this definitely smells like the former based on what little information I have.
But being on the receiving end of such an event tends to suck baseballs through a carbon nanotube straw either way, and believe me that you have all of my sympathy and my nerding out trying to analyse how said event came to pass was, just, well, just as much a result of having waded through similar swamps previously myself as the sympathy :)
As a side note, the requirements in open-source licenses (such as redistributing source yourself, giving attribution, etc.) are only enforceable because of intellectual property. Someone owns the copyright, and often has contributors assign the copyright to them, and they then own the IP. The license grants you conditional authorization to distribute the software, provided you comply with certain requirements. If you fail to do that, it's the copyright holder that can really sue.
See Audacity. Open source but the name is registered trademark and owned by the Muse Group
https://www.audacityteam.org/copyright/
https://github.com/audacity/audacity
Or Blender also another open source project but registered trademark
https://www.blender.org/about/logo/
https://github.com/blender
Krita too
https://krita.org/en/item/krita-trademark-policy/
https://invent.kde.org/graphics/krita
There are countless examples