Add note re only adding tests with Free Software fonts
diff --git a/test/shaping/README.md b/test/shaping/README.md
index 050ae13..bf09909 100644
--- a/test/shaping/README.md
+++ b/test/shaping/README.md
@@ -30,8 +30,11 @@
$ ./hb-unicode-encode 41 42 43 627 | ./record-it.sh ../../util/hb-shape font.ttf >> tests/test-name.test
```
-If you created a new test file, add it to Makefile.am so it is run.
+If you created a new test file, add it to `Makefile.am` so it is run.
Check that `make test` does indeed run it, and that the test passes.
When everything looks good, `git add` the new font as well as new
test file if you created any. You can see what new files are there
by running `git status tests fonts/sha1sum`. And commit!
+
+*Note!* Please only add tests using Open Source fonts, preferably under
+OFL or similar license.
