> You can have different products using the same name so long as they're not in the same category.
Usually that is taken as meaning categories such as 'beverages' vs 'cars'.
Trying to extend it to saying 'my three-wheeled car product called Ford Focus is in a different category to that four-wheeled one' would be unlikely to succeed
A recent example in the software domain was Python ( cloud services ) versus Python ( the language ). Python cloud services is now called Veber Cloud.
Using the same name as another software product may be allowed legally, but it's still a terrible idea to name your company/product in such a way that it becomes nearly impossible to even discover.
according to the technicality of trademark law, it's probably okay (depending on how good the lawyers are - in some cases a court desides that "technology" counts as a market, in other cases they want to get super specific). from the perspective of being able to find your product in a search engine or just generally not being a dick, whoever made this calibre took the name of the ebook software.
You can have different products using the same name so long as they're not in the same category.
So the guy who made this software isn't "taking someone else's name", he's using a name that isn't being used in that category (AFAIK).
Background: I once had to settle a trademark infringement case.