<br>As for trademark issue, there are other themes/templates named "Infinity" at Themeforest as well if you search the site - though I doubt those clash with the auto updates of both themes. As David mentioned above, Infinity is a generic word.<br>
<br>As I see it, the theme name "Infinity" is yours as far as official WP Theme Repo is concerned, no trademark issue is involved here. As Kirk mentioned above, it's great that you want to help them, you can forward the code they could use to avoid auto-update clash with your theme.<br>
<br>Cheers.<br><br><br>