lol good one! Have you SEEN mylaps.com?
Sorry if I'm overly cynical.
The problem with an open source design is that a) the software system has to WORK. Track/group organizers can't be futzing around with hobby level software. Yes of course there is some absolutely great open source software but something this niche ain't gonna attract those developers, and software needs constant maintenance, which is a huge problem with open source if you don't have huge market share / momentum. Of course I don't know how well (or not) the AMB software works.
Second, even ignoring those problems, someone has to build compatible transponders. In an open source, patent free world, who is going to take that on if they think the field is wide open to any other manufacturer to come along? For very large markets this is fine, but for the limited number of sales that this market has, plus the problem of having to displace AMB, I just don't see it happening.
I do see that the westhold transponder is $170 vs $500 for the AMB. Probably $10 BOM and $40 to package it, so right there you can witness the power of a monopoly. I personally don't mind paying for quality products, but that is just gouging. The subscription on top of that, is frustrating.
What might work, assuming the AMB design is not patent encumbered, is an open source hardware design. You could buy a premade board on sparkfun or wherever. Then it's up to the individual racer if they want to DIY. I could see that the X2 might have some kind of digital signature such that it doesn't work when the sub is "expired", but to the extent that AMB still supports legacy non-authenticated transponders, a DIY hardware design might be feasible.
Maybe I'm wrong on how hard it is to build a transponder. ie, if very precise antenna or other such things are required, that are beyond DIY capability. I mean, it is millisecond timing.
And anyway, my frustration is purely theoretical. I only have old style, non-subscription transponders. I know I need another one this year so I bought it now just in case.