I favor practical organization. I'm not claiming that users don't have the right to post products in the "User Contributions" category, nor am I arguing whether or not the definition of "contribution" partially validates that right. I don't think that a system that mixes "free contributions" and "commercial products for sale" is optimally organized. If I am searching for quality "commercial" products for sale for independent developers, maybe I don't want to wade through incomplete or inferior freebies of less than "commercial" quality. Alternately, maybe I am on a strict budget and am merely browsing through "freebies", perhaps, because I hope I might find something that might be useful later. I may not want to search through "commercial" products for sale when searching for freebies. I think that maybe the items might be more properly organized with two thread categories, something similar to: "Free User Contributions" and "User Products for Sale".

I think that the majority of the items in "User Contributions" are free, so there might be certain assumptions. Regardless as to actual intentions, people don't like to feel fooled, temporarily or otherwise. Some individuals might feel fooled when clicking on what they may have thought was a "free contribution" but was instead, an "advertisement for a product". This might be similar to selecting an item for reading which looks like normal email correspondence, but is actually spam.

If I was searching for quality "commercial" resources to purchase, I probably wouldn't even bother searching in the "User Contributions" thread category, unless I had accidently encountered items for sale when looking for freebies, which I remembered. In such a case, I would then have to wade through the "freebies" to find the actual product I remembered seeing accidently.

If you are searching for products to purchase, you may not want to waste your time searching through that which may be irrelevant.
If you are merely browsing for "freebies", you may not want to waste your time searching through that which may be irrelevant.

Of course, it may be in the interests of those that are selling products to post "advertisements" everywhere possible.