Add a couple gfonts copyright rationales

com.google.fonts/check/metadata/copyright_max_length
com.google.fonts/check/metadata/nameid/copyright
On the Google Fonts Profile.

(PR #4570)

CHANGELOG.md

@@ -45,6 +45,8 @@ A more detailed list of changes is available in the corresponding milestones for
   - **[com.google.fonts/check/metadata/nameid/family_and_full_names]:** Added rationale. (PR #4570)
   - **[com.google.fonts/check/metadata/match_name_familyname]:** Added rationale. (PR #4570)
   - **[com.google.fonts/check/metadata/canonical_weight_value]:** Added rationale. (PR #4570)
+  - **[com.google.fonts/check/metadata/copyright_max_length]:** Added rationale. (PR #4570)
+  - **[com.google.fonts/check/metadata/nameid/copyright]:** Added rationale. (PR #4570)
 
 #### On the FontValidator profile
   - **[com.google.fonts/check/fontvalidator]:** Added rationale. (PR #4570)

Lib/fontbakery/checks/googlefonts/copyright.py

@@ -96,6 +96,12 @@ def com_google_fonts_check_glyphs_file_font_copyright(glyphsFile):
     id="com.google.fonts/check/metadata/copyright_max_length",
     conditions=["font_metadata"],
     proposal="legacy:check/104",
+    rationale="""
+        We check that the copyright notice within the METADATA.pb file is
+        not too long; if it is more than 500 characters, this may be an
+        indiciation that either a full license or the font's description
+        has been included in this field by mistake.
+    """,
 )
 def com_google_fonts_check_metadata_copyright_max_length(font_metadata):
     """METADATA.pb: Copyright notice shouldn't exceed 500 chars."""
@@ -113,6 +119,10 @@ def com_google_fonts_check_metadata_copyright_max_length(font_metadata):
     id="com.google.fonts/check/metadata/nameid/copyright",
     conditions=["font_metadata"],
     proposal="legacy:check/155",
+    rationale="""
+        This check verifies that the copyright field in METADATA.pb matches the
+        contents of the name table nameID 0 (Copyright).
+    """,
 )
 def com_google_fonts_check_metadata_nameid_copyright(ttFont, font_metadata):
     """Copyright field for this font on METADATA.pb matches