Why is it an empty gesture?
Because it was not "released to the public" in the normal and generally understood sense in which that phrase is applied. This source code has been made available
(i.e. licensed) to individuals
who agree to some frankly restrictive licensing terms. Hardly the same as "released to the public" in my world. And I doubt I'm the only one on that planet.
I half suspect this release is intended to give Microsoft an excuse to go after virtually any text processing app with the argument that "they must
have borrowed some
intellectual property from Microsoft" by sheer virtue of the fact Microsoft's source code has been published.
If it sounds crazy, take a look at all the "presumption of piracy" arguments that are being advanced by large corporations and industry groups in support of ridiculous new laws they're lobbying for.
Sorry for sounding cynical. But I really do think the only reason this code is being released is to establish "primacy" and set the stage for charging opponents with "knowing infringement" in future legal battles.