Thank you for pointing this out, I forgot this specificity of duplicacy. I added a disclaimer: https://github.com/christophetd/duplicacy-autobackup/commit/...

Regarding the license of my code I'm unsure what to use. The license of duplicacy (https://github.com/gilbertchen/duplicacy/blob/master/LICENSE...) states that "Modification and redistribution are permitted, but commercial use of derivative works is subject to the same requirements", so it seems to me that as long as I include such a disclaimer, it should be fine. I opened an issue on the duplicacy project to ask the author his opinion.