you should read the EULA (end user license agreement) that shows up when you submit a filter. that should answer most of those types of questions.
in addition to that agreement, we do borrow each other's filters or parts of filters. as you get familiar with FF you'll notice a couple of categories called 'snippets'. these were submitted by users for exactly that purpose, to be used by whomever wants to in their own filters.
however, you'll also find that there's a bit of a 'filter etiquette'. if you use part of someone else's filter, you should say something in the description of your filter that gives credit to the person that created that part you borrowed. it's just a common courtesy to do so.
and as for JUST changing the presets and re-submitting the filter, i wouldnt. change the components if you like, but if you JUST change the presets you're really not creating a new filter.
you can download filters and make your own presets and include them on the filter you downloaded, but dont just upload the same filter with new presets. someone would most likely complain and your filter would most likely not be accepted.
but if you went into the editor and re-did the filter and changed it significantly and then saved that and submitted that as a new filter, it will most likely be ok. just include something in your description that gives credit to the original maker of the filter.
i realize you do not natively speak english, so i hope we understand each other.
most of my filters are from scratch. but, i have used parts of others filters in some. if you read the descriptions of my filters you will find a few where i have given credit to others for their part of my filter.
by the way, your english is a LOT better than my japanese