Michael Byrne, writing at Vice's Motherboard, details the Open Sourcing of License Plate Tracking bits...

OpenALPR works well and fast, at least judging by the demo. It's also legal for the most part. As EFF lawyer Jennifer Lynch tells Ars Technica, "While a handful of states have passed laws explicitly restricting private citizens and companies from using ALPR technology, outside of those states, there is not much in the law that would prevent someone from using the technology unless its use rises to the level of stalking or harassment. License plates are exposed to public view, and ALPR companies like Vigilant consistently argue they have a First Amendment right to photograph plates and retain the data they collect." - via Michael Byrne, writing at Vice's Motherboard