I just released the first alpha version of my JSON Parser/Encoder Ktuo. I use it in several projects with no problems at all. However, this is still an alpha release, so be aware that you may run into issues. The download area for Ktuo is here. A bit of documentation for the project is here.
I know the question of why another JSON parser is going to come up, so I am just going to go ahead and address it now. The existing JSON parser is still available and still useful. It makes elegant use of continuations to handle cases where it may not have a full JSON expression available. This makes it very flexible and pretty darn interesting. However, these extra features also add significant complexity and no small amount of additional resource usage. While working on my Tercio project I realized that I didn't need these features and I didn't want to pay the cost of the complexity and resource usage overhead. So I wrote my own. Eventually, I realized it was useful in and of itself and created a project space for it.