I wish I was open to use whatever software I wanted…
The problem (outside of knowledge alone… LOL) is…
I do not know of any platform that will:
1.) Do/provide a LIVE feed
2.) Allow overlays/animation
3.) Allows external communication for real-time display updates on the HUD display.
I’ll out myself here… hahaha…
but before I do… disclaimer.
*I know this is largely not supported.
*I know it has security issues.
But I am using Flash (Adobe) for the current video feed and overlay, animations.
Supports external webcam feeds
Allows me to do whatever animation or overlays I want (visuals, menus…etc)
I have installed LAMP… so I am using a mix of PHP and Flash (ActionScript) socket connections to communicate back and forth, to communicate between the ‘outside data’ and the RPi/Flash platform.
This being an off-line (so to speak) prop/project… the security stuff if not a huge issue/concern
** Same with my BarBot project! (I’ll post on that soon too!) 
** Off to read up on OpenFace!
Thanks for the link
Edit:
I just saw: Python
So already looks like it could be a replacement if I cant get the current Flash to ‘play ball’ lol