- Red Hat asked people to rename unofficial RHL distributions something like Pink Tie back in the day, and the tradition continued with CentOS and the like.
- Firefox has a different tack, and just makes sure people sign up to meet certain specs to be able to use the trademark. That might mean not diverting from upstream too much (eg, Debian wanted FF to use Linux FHS standard, FF upstream didn't do that, hence Iceweasel).
Not a lawyer etc.
* The firefox branding itself is non-free, which is unacceptable for debian * The replaced the branding, but kept the name first * Mozilla complained and clarified that a program called "Firefox" has to bear the official logo
Detailed:
http://en.wikipedia.org/wiki/Mozilla_Corporation_software_re...
So the new name is not so much deliberately chosen to provoke confusion as it is to reduce confusion.
source: worked there
Edit: the title of this submission should really be "10gen: the MongoDB Company shortens their name to MongoDB, Inc." Less attention-grabby, more truthy.