@taciturasa, hmm, I’ve studied the source icon and can’t see a fold shadow… it’s an old icon, so possibly the artist did it before the guidelines had settled into their final form?
My inspection did highlight two things that are visible in the largest icon size:
- The absolute white of the Circle of Friends is a bit “stark” compared to the Software icon (which uses a slightly peachy “off-white” for the letter A glyph);
- The Circle of Friends lacks the subtle drop shadow, which is visible when you view the Software icon at the largest size.
I’ve now incorporated these tweaks into the largest version of my icon. I think I might struggle to do a more pixel-perfect forgery of the source style 
but I welcome feedback if I’ve missed anything.
EDIT: due to quality reduction of the embedded image, neither icon looks quite as nice as the one on my own PC sadly, but hopefully you can at least see that they match!