1) You cannot release the passive key grab, but you can disconnect the signal you connect to in enable(). This is important in particular because otherwise enabling multiple times is not idempotent. 2) There is no ~/bin/area-screenshot-post (and there cannot be), so you can/should remove the code to invoke it. 2) If you return the AreaScreenshot object from init(), you can avoid writing enable() / disable() at global scope.

1) You are right, didn't think about just disconnecting the signal. 2) There is no "~/bin/area-screenshot-post" by default, but you can place one there (see: https://github.com/DASPRiD/gnome-shell-extension-area-screenshot/blob/master/README.md). 3) Great, would be nice if such stuff could finally be documented.

Uhm, in that case, it seems ok to me. (As for documentation, you have the code, and patches are always welcome!)