3rd-party just seems to be a reincarnation of 3PP, a tag that was previously burned. This tag seems to be used in the exact same way and have the exact same issues as the previously burned tag.
The original was burned for a lot of reasons, but the big one in my mind is that tags are not meant to categorize where the content of the question comes from, but what the content of the question actually is in a way that makes it easy for people to browse topics of interest to them.
Unless there is some shift and 3rd-party is suddenly a useful concept for us, I think the tag should be burned.