[troy_dietz]

With enough modification, it would be "legal".
The only issue is that it would require completely recreating the logo in such a way that there is a very clear difference between the original and your creation, but then you miss the point of creating a "parody" button in the first place.

Because you wouldn't be selling them (at least, I assume so) and they wouldn't be very widely distributed, you fall into a bit more of a grey area.

If you really want to make a "STEAMBorks" button/pin, you could find a similar font and write the name near the top, and them outline the entire image with a ring gear.