WORLD LAND: Natural Earth, 1:110m physical land, public domain.
Source: https://github.com/nvkelso/natural-earth-vector/blob/master/geojson/ne_110m_land.geojson
Terms: https://www.naturalearthdata.com/about/terms-of-use/

AUSTIN ROADS: U.S. Census Bureau TIGERweb Transportation service, layers
2 (primary), 6 (secondary), and 8 (selected central Austin local roads).
Public domain U.S. government geographic data. Local extract, generalized,
with attributes removed. Coverage is selective; not for navigation.
Source: https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Transportation/MapServer

Austin city plate: original schematic vector illustration for NPC Atlas.
The plate is decorative and is not surveyed geographic data.
Leaflet is distributed separately under its BSD-2-Clause license.