I'm one of the developers of TGMPA.

> The TGM Plugin Activation class has since been updated despite the version number not being changed.

That's misleading, but it would explain the wording in GitHub Issues we've been getting.

The currently tagged release is 2.4.0 and has been for over a year. As per typical git-flow development, we've got a hotfix/2.4.1 branch which should be merged with the master branch, tagged and released within 12 hours from now. It's at that point we'd recommend theme and plugin developers update.

The confusion is that we've also already merged the changes (including version number bump) into the develop branch, and at the same time, switched the default branch on GitHub to be develop - this is the branch you see when you look at the repo on GitHub.

The master branch also erroneously had commits made since 2.4.0 was released. These have been replicated in the develop branch, and the master branch will be reset to the 2.4.0 commit before the 2.4.1 merge.

The one main erroneous commit was regarding the removal of the deprecated screen_icon() function. This will be fixed, along with a load of other improvements, in a tagged 2.5.0 release which is due sometime in May, when it's ready.

As always, just like WPORG plugins, we recommended only including code from tagged TGMPA releases in your theme and plugin releases. We do appreciate the bug reports and improvement suggestions from those who use the develop branch.