Currently,

lang/en/plugin.php:$string['filtercontribonly'] = 'Show contributions only';
lang/en/plugin.php:$string['filtercontribonlyactive'] = 'Showing contributions only';

I believe these should be:

lang/en/plugin.php:$string['filtercontribonly'] = 'Show add-ons only';
lang/en/plugin.php:$string['filtercontribonlyactive'] = 'Showing add-ons only';

or perhaps it might be even better to change the language in the code as well so that references to contrib are changed to addon. Then we might have something like:

lang/en/plugin.php:$string['filteraddononly'] = 'Show add-ons only';
lang/en/plugin.php:$string['filteraddononlyactive'] = 'Showing add-ons only';

Peace - Anthony