diff --git a/Modules/CMakeAddNewLanguage.txt b/Modules/CMakeAddNewLanguage.txt
index 6a30dd88b..612e1a3a5 100644
--- a/Modules/CMakeAddNewLanguage.txt
+++ b/Modules/CMakeAddNewLanguage.txt
@@ -1,3 +1,19 @@
+This file provides a few notes to CMake developers about how to add
+support for a new language to CMake.  It is also possible to place
+these files in CMAKE_MODULE_PATH within an outside project to add
+languages not supported by upstream CMake.  However, this is not
+a fully supported use case.
+
+The implementation behind the scenes of project/enable_language,
+including the compiler/platform modules, is an *internal* API that
+does not make any compatibility guarantees.  It is not covered in the
+official reference documentation that is versioned with the source code.
+Maintainers of external language support are responsible for porting
+it to each version of CMake as upstream changes are made.  Since
+the API is internal we will not necessarily include notice of any
+changes in release notes.
+
+
 CMakeDetermine(LANG)Compiler.cmake  -> this should find the compiler for LANG and configure CMake(LANG)Compiler.cmake.in
 
 CMake(LANG)Compiler.cmake.in  -> used by CMakeDetermine(LANG)Compiler.cmake