The EULA really says that you can do that, even just render a filter and sell, no problem.
I think you read the
slightly infected debate that rose from the fact that someone did what is legally OK, but I among others thought it was immoral (which is now corrected btw).
I do not speak for FF Inc, I am just a filter maker, and I really do not see any problem with what you want to do neither legally/EULA wise, nor morally.
Welcome btw, and please do not hesitate to ask questions on filter making, it is fun and you will get hooked, I promise. Maybe too hooked. Sometimes I think there is a business opportunity for a FWA (Filter Weavers Anonymous)

- I never expected the Spanish inquisition