Doc: add links to NumFOCUS GDAL page

GOVERNANCE.md

@@ -0,0 +1,4 @@
+Governance
+==========
+
+The governance of the GDAL project is described by [RFC 1: Project Management Committee Guidelines](https://gdal.org/development/rfc/rfc1_pmc.html)

README.md

@@ -29,6 +29,26 @@ GDAL is an open source X/MIT licensed translator library for raster and vector g
 * Wiki: https://trac.osgeo.org/gdal - Various user and developer contributed documentation and hints
 * Mailing list: https://lists.osgeo.org/mailman/listinfo/gdal-dev
 
+[//]: # (numfocus-fiscal-sponsor-attribution)
+
+The GDAL project uses a [custom governance](./GOVERNANCE.md)
+and is fiscally sponsored by [NumFOCUS](https://numfocus.org/). Consider making
+a [tax-deductible donation](https://numfocus.org/donate-to-gdal) to help the project
+pay for developer time, professional services, travel, workshops, and a variety of other needs.
+
+<div align="center">
+  <a href="https://numfocus.org/project/gdal">
+    <img height="60px"
+         src="https://raw.githubusercontent.com/numfocus/templates/master/images/numfocus-logo.png"
+         align="center">
+  </a>
+</div>
+<br>
+
+NumFOCUS is 501(c)(3) non-profit charity in the United States; as such, donations to
+NumFOCUS are tax-deductible as allowed by law. As with any donation, you should
+consult with your personal tax adviser or the IRS about your particular tax situation.
+
 ### How to contribute
 
 See [CONTRIBUTING.md](CONTRIBUTING.md)

gdal/doc/source/sponsors/index.rst

@@ -164,9 +164,15 @@ the health of the project:
 
   </script>
 
-The GDAL Project is hosted by `OSGeo <https://www.osgeo.org>`__, and
-`NumFOCUS <https://numfocus.org>`__ will serve as the fiscal sponsor once GDAL's application is completed,
-enabling all sponsorship to go through a 501(c)3 as charitable donations.
+The GDAL Project is hosted by `OSGeo <https://www.osgeo.org>`__,
+and a fiscally sponsored project of `NumFOCUS <https://numfocus.org>`__, a
+nonprofit dedicated to supporting the open-source scientific computing community. If you
+like GDAL and want to support our mission, please consider making a
+`donation <https://numfocus.org/donate-to-gdal>`__ to support our efforts.
+
+NumFOCUS is 501(c)(3) non-profit charity in the United States; as such, donations to
+NumFOCUS are tax-deductible as allowed by law. As with any donation, you should
+consult with your personal tax adviser or the IRS about your particular tax situation.
 
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