Devil's advocate:<p>Your software is often used in conjunction with zendesk, you say it yourself and they both use "zenX" branding.<p>To me that could easily lead to confusion as a customer might believe they are are part of a suite of SaaS offerings under the "zen" brand (i.e. zendesk branching out).<p>I make no comment on the rest of the story, just that specific bit.<p>[Edit]: Maybe I should have said 'low-ranking imps advocate' instead :p
This is one of the more reasonable trademark defenses by one of the "big guys" that I've seen - one they are <i>required</i> to defend in order to keep. So, though it hurts, you pick a new name and move on. Very possibly the lawyers told the CEO to not respond to those emails until a decision was made.<p>As an aside, the post starts by saying "it's not something to get worked up about" -- and then proceeds to do nearly exactly that, detailing even his email "exchange" with the CEO.
Apparently they think they own zen <i>and</i> desk.<p>See <a href="http://www.ripoffornot.org/" rel="nofollow">http://www.ripoffornot.org/</a>
If I was Zendesk, I would do exactly that, fight your trademark. Not that their objections will necessarily hold up. You could arguably defend it, but why bother?<p>If you say you are friendly with Zendesk, why did you name your product Zen-something if there is no strict affiliation between the companies, it doesn't make any sense, it should be lesson for others. The thing is that "being friendly" is not really tangible in legal terms. In fact it's the "being friendly" part that probably brought this on because if Zendesk hadn't heard of you and their customers weren't using Zenbilling then your application would probably have done through without hassle.<p>I know, and probably Zendesk do too, that what they are doing isn't strictly "nice" to you. But there wasn't any official partnership or other deal or agreement in place and that ultimately means there is no relationship between the companies.<p>What you are doing is right, find a new name and move on. But don't let it spoil your "friendship", and although probably there's no room for "favours" anymore, keep your mind open for mutually beneficial agreements instead.
What if Zend comes out with software called Esk? That would be super confusing between Zendesk and Zend Esk, so it would be better if you changed it before Zend does that.
I think if people believe that anyone using names that have been used for hundreds and thousands of years are going to preempt everyone else from doing so (zen, book...) they should not have used those names in the first place. If you want to prohibit all derivations of your name the rule should become that you have to make up a completely new word. If you chose a commonly known word then don't expect to prohibit everyone else from doing so.
Maybe consider yourself lucky that you'll be prevented from ludicrously associating your business with the word Zen although said business is, as a provider of rationalist technology, almost by definition completely at odds with the school of Buddhism by that name.<p>In any case, the victimized tone of the article is about as un-Zen as it gets.
Zen has been around since the 6th century, I understand from a legal perspective but it's a terrible position to be in.<p>Its a pity for innovation that this can be done through financial means rather then hashed out between the parties.