Document four more NPS-adjacent resources

- national-park-service/fonts: unofficial but genuinely open (SIL OFL
  1.1) typefaces inspired by public-lands signage -- unlike the
  proprietary Rawlinson/Frutiger this app already ruled out, this one
  has no licensing blocker if the look is ever wanted in this app's
  own UI chrome.
- The official NPS Data API (developer.nps.gov) -- a legitimate
  government data source, separate from the Mapbox-Atlas-licensed
  tile service. No current use case (this app isn't NPS-park-specific)
  but worth remembering.
- Two hobby projects (carlknutson/nps-changes-site,
  seankelliher/us-national-parks-alerts) noted as real-world examples
  of consuming that API, not as reusable libraries.

docs/nps-resources.adoc

@@ -246,6 +246,19 @@ own work (a map viewer, not a publisher of NPS-branded content):
   Adobe Systems). Both proprietary/commercially licensed, unlike the
   fonts this app already vendors (Noto Sans, SIL OFL — see
   `docs/third-party-notices.adoc`) — not something to pull in.
+* *A genuinely open alternative*: https://github.com/national-park-service/fonts
+  — despite the org name, its own `DISCLAIMER.md` is explicit that this
+  is an **independent, unofficial** project, "not affiliated with,
+  endorsed by, or sponsored by" NPS, and that its six typefaces (NPS
+  2026, Redwood Serif, Campmate Script, NPS Symbols, Sequoia Sans,
+  Switchback) are original works "inspired by" public-lands signage —
+  explicitly *not* reproductions of Rawlinson or anything NPS actually
+  owns. SIL OFL 1.1 licensed, same family of license as the fonts this
+  app already vendors. Unlike Rawlinson/Frutiger above, this one's
+  actually usable if the NPS-inspired look is ever wanted in this app's
+  own UI chrome (currently plain system fonts, `public/css/style.css`) —
+  no current use case, but no licensing blocker either, worth
+  remembering if that comes up.
 * *Hawaiian typography*: NPS Rawlinson includes vowels with Hawaiian
   macrons (ā, ē, ī, ō, ū) and the okina (ʻ); the regular weight of
   Frutiger doesn't, so NPS uses a separate "HFrutiger" weight for
@@ -306,3 +319,27 @@ OSM-derived data, just a different source. No current need, and unlike
 everything else in this doc (CC0, BSD, MIT, public domain) this repo has
 **no `LICENSE` file at all** — its terms are genuinely unclear, so treat
 that as a blocker too, not just "no use case yet."
+
+=== NPS Data API (developer.nps.gov)
+
+A separate thing from the tile/Park Tiles service above — a general
+government open-data API (parks, alerts, campgrounds, places, ... —
+official docs: https://www.nps.gov/subjects/developer/api-documentation.htm,
+a JS-rendered Swagger UI that doesn't render via a plain fetch; a free
+API key from that same page is required to call it). No current use
+case (this app isn't NPS-park-specific — park4night POIs and personal
+GPX/FIT tracks, not NPS units), but it's the legitimate, non-Mapbox-Atlas
+government data source behind it, worth remembering if a "show nearby
+NPS park info/alerts" feature ever comes up — the `wms`/`source-arcgis-rest`
+npmap5-plugins entries above would be the MapLibre-side plumbing for it.
+Two hobby projects (both MIT, not NPS-affiliated, not directly reusable
+as libraries — noted only as real-world examples of consuming this API)
+turned up while looking at this:
+
+* https://github.com/carlknutson/nps-changes-site — a React/Leaflet
+  explorer for all NPS sites, most fields sourced from this API
+  (supplemented by manual/AI-assisted research for fields the API
+  doesn't have), data refreshed daily via GitHub Actions rather than
+  called live.
+* https://github.com/seankelliher/us-national-parks-alerts — a
+  Vue + Express directory of park alerts, pulled live through this API.