I found this on the github.
There seems to be another way to get tux.https://github.com/ValveSoftware/steam-for-linux/issues/1815
too many complains over a virtual item that has no game-changing effect in the game itself and isn't even trade-able to begin with.
Well, there's a reason for that.
1. First, it tries to draw new Linux users.
2' Second, Tux is a gift to the Linux community who pushed for a Linux client and beta tested TF2's client.
3. Third, Tux is the linux mascot. By not using linux, but equipping Tux, you misrepresent yourself to others for an item that, as you said, is not able to be traded nor does it make any change to the game and....
4. It violates the Steam Subscriber Agreement.
Valve is looking into this, and its not about people who just install linux, and then remove it.