I think it is dependent on the game being installed on your machine to get the graphics and dependency information. I am not sure but I don't think you can download just the editor.
all the data files that the editor uses are so tightly integrated into the game data files that if you were to theoretically download the editor you would practically get the entire TFT expansion pack anyway. So no, there is no real such thing as a "standalone TFT editor".
And technically the TFT editor is not free anyway, Blizzard says it is an extra, but in reality part of the money you pay goes towards the editing tools.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory