Interesting, hope you get this sorted out. I really like this kind of projects.
Since I am using the seedsigner I have heard also the fud around it from Coinkite, although not enough time to see everything.
Capitalism is about competition, so for me it is fair game.
However I can understand that he could get pissed off if you reversed engineered his clock and didn't put credits. But according to you this is not the case, so I would just write "inspired from Coinkite" and put a link. Sometimes I do the same for algorithms, if I had troubles and found a good algorithm from someone else I put a link to Stack overflow in a comment haha.

In the Bitcoin community I have heard also unjustified fud about Ledger too, sometimes Trezor also, and seedsigner as written above, so I guess it may be a problem with how people react on social networks. In my case, I just ignore it. In this regard, Blockstream is a very good company, they produce hardware and tell us how to replicate it and don't get upset about it. It is purely open source.