Including Osmic icons into JOSM.
This style only affects POI icons. You will still need the JOSM standard style (or any other) enabled.
Go to JOSM's preferences, select the 3rd icon from the top, select Map Paint Styles Tab, then select Osmic. More detailed instructions are available in JOSM's documentation.
The style file is the same license as JOSM, which is GPLv2+ (https://github.com/openstreetmap/josm/blob/mirror/LICENSE). Icons are CC0 from Osmic.