Open source has its place, but generally no manufacturer will employ it were it can lead to serious product liability issues. For example, car manufacturers have been adamant that only properly licensed mechanics be able to access a car's software. Part of the reason for this may be to ensure commercial advantage against non-licensed mechanics, but a serious concern they point out is that modifying the software can make a car dangerous and a car owner may have no idea what modifications have been or their effect until it is too late. For the same reason, I doubt e-cig manufacturers will have any more interest in such an idea. All you need is one person modifying the code so that the product works in an unsafe manner, such that the manufacturer ends up with a big black eye from the resulting media coverage or lawsuit.
