I am going to open this can of worms right here.
When does inspiration become plagiarism for craftsmen? I think it is a subjective matter and it depends which tradition you come from. For me the answer is: rarely if ever.
Let me explain. In my opinion, craft is not art. Craft is the skillful production of items that often perform a function. Since f.ex. teapots are functional, there are rules concerning their design (position of spout, handle etc). Some are flat, some are round, some are square and others are pumpkin-shaped etc but they all adhere to certain rules or they would not be functional. Within these strict givens, the craftmen are free to play around.
I copy forms I like from all around. My brain is always fishing for ideas and inspiration - I search the internet, I shamelessly model my pieces on the Song items in the British museum, I "steal" inspiration from everywhere, but I always put it all together into something that has my DNA on it.
When I was studying for my Ph.D. in modern Chinese literature at Princeton, my teacher told me not to be afraid of picking a thesis topic that "had already been done" because, as he said, nobody thinks alike and anything you do will always come out differently from others who work on the same subject matter. I never finished my Ph.D. by the way, but this is probably the most important lesson I learned at Princeton (most of the rest I have gladly forgotten!).
In potting, if I am inspired a lot by someone or if I modify a glaze I have found, I always note the source of the original. Maybe a habit from my academic training. That's just done, I think.
In the Chinese tradition, copying - even plagiarism - has a noble tradition. Aspiring intellectuals and mandarins were judged on the merit of their ability to copy and imitate the canonized masters. There is an informal tradition for this in pottery, too. In my teacher's studio in Taipei, every tianmu bowl we made was held up to some elusive ideal standards. Everything seemed to fall short of that and still we kept trying to make "the" tianmu bowl. I think Chinese ceramic aesthetics is very strict partly because there is always thought to already exist a perfect example of what you are trying to make. You are not a pioneer, ever.
So, if you look at my current source of inspiration, Yohei Konishi and his student/ follower Taisuke Shiraiwa, first of all I think it is important to remember that they are not alone, nor are they pioneers. They have merely found an expression within a tradition. That is not to belittle their work; on the contrary, that's the stuff 国宝 (national treasures) are made of. Their work is amazing! TRULY INSPIRATIONAL. Their technical skills are considerable. Where their work is naturally loose, mine is tight (I have to thrown thickly and trim a lot in order to achieve the thinness of my pots). Where their work has been licked by the flames, mine is merely heated by electrical elements. Where their work is from the local soil they probably step on every day, mine is a mix of commercial porcelains. And so on and so on. There are as many differences as there are similarities. And that's the wonderful part. We can breathe life into tradition if everyone would be MORE INSPIRED!
Kaneshige Michiaki (1934-1995) said of tradition: Tradition is sometimes confused with transmission. Copying Momoyama pieces is transmission. Producing contemporary pieces incorporating Momoyama period techniques is tradition. Tradition consists of retaining transmitted forms and techniques in one's mind when producing a contemporary piece. Tradition is always changing. A mere copy of an old piece has not changed; it is nearly the same as its prototype of four hundred years ago. Tradition consists of creating something new with what one has inherited.