Kontakt 5 Player is a free musical composition suite aimed at professionals based on Native Instrument's own Kontakt technology.

Kontakt 5 Player is a Lite version of Kontakt 5, which is the full version of the app. It's suitable for basic composition but not for much more as the editing features in Kontakt 5 Player are disabled and many of the samples are limited demos only.

You're also limited to what type of libraries you can import into Kontakt 5 is only worth trying if you're going to upgrade.