YouTube Osho Channel Copyright

I have a YouTube channel where I am making animation based on master Osho's discourses. I am not using any direct /modified voice, photos, videos of Osho. These animations are my own interpretations/ understanding of his mediation techniques. Does it call any copyright violation as I have got an email from a Very renowned foundation claiming Osho's copyright? As per my understanding and research over the internet, Osho's name, his thoughts, and knowledge comes under the public domain and no proper documentation is available anywhere in World clearly stating Osho handing over his IP Rights. Kindly advise. Thanks in advance