In fact, this app is for "Downloadable computer software for modifying and enabling transmission of images, audio-visual and video content; downloadable computer software for viewing and interacting with a feed of images, audio-visual and video content and associated text and data; computer software for social networking. "
https://en.wikipedia.org/wiki/Apple_Corps_v_Apple_Computer
though, in your example, i'd have to wager the Windows trademark extends way further than just "operating systems". "computing" at large seems more likely.
The word "gram" is much less unique in the areas of communication and delivery. After all, it's derived from telegram. Instagram is not only something-gram communication service. (And it's not the only insta-something either)
This is why windows is a nonsense trademark even in reference to computer software but Microsoft Windows is reasonable.
For a previous exploration of this issue see the Lindows linux distro legal fight which Microsoft lost.
Good point on the Lindows overreach.