Project OutFox supports all NoteSkins that are compatible with 5.0 and 5.1 (excluding 5.2).
To install them, extract their folders to
Appearance/NoteSkins/dance in your installation directory, or your profile folder.
Project OutFox is an extensible rhythm game engine based on StepMania, featuring 18 different modes simulating different dance, instrument, and key-based rhythm games.
Its goal is to create a cross-platform “sandbox” and “museum” for the genre, supporting over 20 years worth of content across a variety of formats.