Absolutely under no circumstances can you upload a pattern that you do not own the rights to. It does not matter if it is a free pattern from another site. Do not upload it. If you want to tell the members of the forum where they can find the pattern that's fine. If you created the pattern make sure you are not violating any trademark or copyrights. For example, uploading a pattern of the Harley Davidson emblem is a no-no. Disney characters, WWE, Nascar, NFL, school mascots etc... are all on the forbidden list.