Sorry for late reply, was very busy. Thank you for your interest of usage on my asset.
Basically, I still don't have the answer for usage on open source.
Regarding usage of 3rd party assets of the open source project, I did some quite researches for a while but still hasn't found conclusive answer yet specifically from unity asset store as example (since that's the search result I managed to find). The answers I got were vary.
Some suggests that if you can exclude the assets from being distributed on the open source, then it is fine. In that case, you can use my assets if it can be excluded when distributed on open source.