Make an Outer Glow in GIMP
What you need:
Method A (Faster, easier)
1. Open the file.
2. Go to Filters>Light and Shadow>Drop Shadow.
3. Change the X and Y offset to 0.
4. Change the color to white (or the color you want your glow) and click OK.
5. Go to the Layers dialog (Ctrl+L) and click on the Drop Shadow layer. Press Ctrl+Shift+D until the glow looks right.
Method B (More options, more confusing)
1. Open the file.
1a. If the logo comes close to the edge of the frame, increase the image and layer size using Image>Canvas Size and adding 100px to the height, centering it, and going Layer>Layer to Image Size.
2. Go to Layer>Transparency, and click on "Alpha to selection".
3. Go to Select>Grow, and change the "1px" to "3px".
4. Go to Layer>New Layer, and make it the same size as the PNG.
5. If the layers dialog isn't open, press Ctrl+L on your keyboard.
6. In the Layers dialog, drag the "New Layer" below "Background".
7. Select the Paintbucket tool. Fill the selection with white (or the color you want your glow to be).
8. On the keyboard, type Ctrl+Shift+A.
9. In the menus, go to Filter>Blur>Gaussian Blur, and click OK.
It glows (: