Once called up, the about window cannot be closed until Screem itself is terminated. It's a known problem of the software, cf the URL above.
Created attachment 180122 [details, diff] Patch to make it work Changes: Fixed up the about dialog.
Created attachment 180124 [details, diff] Patch for the ebuild
Created attachment 180228 [details, diff] fix_help_about_dialog.patch Actually, ubuntu fix from http://patches.ubuntu.com/by-release/extracted/ubuntu/s/screem/0.16.1-4.2ubuntu1/ looks simpler.
(In reply to comment #3) Oh, that Canonical illness of not communicating upstream... Yes, their patch is simpler and it works, so take it; thanks for the link. The other one results just in cleaner code: it replaces a series of convoluted calls to a static object by a single dynamic call, taken from a working example in a Gnome project, viz. Dia. As we don't see the code anyway, it doesn't really matter.