Minor Description
json4s-jackson is a Jackson-backed implementation of the Json4s common JSON API for Scala JSON libraries. (Evan Chan has a nice comparison of Scala JSON libraries here: http://engineering.ooyala.com/blog/comparing-scala-json-libraries) It is Apache-licensed, mostly API-compatible with lift-json, and easier for downstream operating system distributions to consume than lift-json.
In terms of performance, json4s-jackson is slightly slower but comparable to lift-json on my machine when parsing very small JSON files (< 2kb and < ~30 objects), around 40% faster than lift-json on medium-sized files (~50kb), and significantly (~10x) faster on multi-megabyte files.