Sure looks like a "tamper proof torx" to me. Hardley propriatory. They can be bought anywhere.
tamper proof torx - Yahoo! Image Search Results
As I said previously "once thiefs know what to look for, all they need is a screwdriver to remove it"
If you have a "special" screwdriver, all they have to do is buy one from you, and carry it in their pocket.
And... if they don't have a screwdriver, a drill and EZ OUT makes it a 2min job.
So you're depending on big burly bike owners to beat up bike thiefs?
And if the owner isn't nearby, it doesn't matter his shape or size.
FYI, bike thiefs are brazen and don't care who's nearby.