https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/6/864971139138302003/

Made this suggestion a few weeks ago

I'm not to familiar with the legalities of it, but i would imagine their items would be copyrighted. http://www.valvesoftware.com/legal.html is valve's legal statements, but they only mention team fortress 2, and the Team Fortress 2 logo, i'm not sure what "team fortress" includes, but i can only imagine everything inside of TF2. An app would be interesting, but i'm not sure what it would accomplish besides bumping trades and posting on others trades. I personally just log into outpost from the web browser and it seems to do the trick. To the best of my knowledge you cant trade on steam VIA tf2 items and whatnot, unless sneeza figured out a system how to.