@zak This is clearly NOT just and oshpark issue. A cursory review of the original post and upverter-made gerber files show that the gerber output is not faithful to the design shown in the upverter eda tool. Further, this issue has be present for more than 2 years!
An export from today shows that text is exported with a border but in the correct geometry. This is gerbv vs. upverter:
An export and produced board from Dec. 2014 show the same bug including on the production board:
Looking at the gerber files for silk and copper layers show that text is exported with an aperture of "%ADD11C,0.2032*%" which means circular with diameter of 0.2032 mm (8 mil). We can confirm that rendering of gerbv is correct by editing the gerbers to use a circular aperture of 0.0 mm diameter and noting that the geometry exported is correct.
The correct way to render text seems to be either a line-based font with user-selected (or scaled) width (aperture), or to render it as you are now but using polygon fills (G36/G37). Please consider using some resources to fix this long-standing bug.