You list Tippingpoint Labs and Held Media Group as "current"--why wouldn't you work there, espcially if you're founder-level at the latter? Surely a serious internship would ask you to step away from your responsibilities at both of those places.
To be fair, I'll probably be part-timing after work at Tippingpoint Labs and HMG, doing mostly development and the occasional remote troubleshoot, unless for some reason I am unable to.
isn't that exactly what's most time consuming and be most responsibility? I feel like saying "just mostly development" is like saying, "I'll just mostly be doing real work" in this context.