This wxJSON release adds support for 64-bits integers on those platforms that have native support for it such as, for example, Windows and GNU/Linux.
You can disable 64-bits integer support if you do not need (or do not want) it. The new version is compatible wih the past: if you do not need 64-bits integers you can still use this new version of the library without the need to rewrite your application.
To know more about the new feature read the this page: