Why is the GnuPG-sign checkbox disabled in SourceTree?

Example screenshot

Using Mac OS X Yosemite (10.10), I cannot active GnuPG-signing of commits in SourceTree, as the checkbox is disabled. How can I enable commit-signing?

How do I turn off Commit sign?

You can disable this by running git config commit. gpgsign false This sets the configuration locally instead of globally.

How do I remove a GPG key from Git bash?

To remote a GPG key from GitHub, go to https://github.com/settings/keys and under GPG keys , select the one and remove it.

You likely aren't pointing the GPG Program setting (found in SourceTree -> Preferences -> Advanced) at the right bin. If you're using GPGTools on OS X, it should be /usr/local/MacGPG2/bin. To navigate to the /usr/bin directory in the Open File dialog, click shift + command + g

SourceTree setting