Hi @ThemeCompare. That’s great feedback - thanks!
Items featured on the Free WordPress Themes landing page (or as the Free File of the Month) now require an additional security audit with the ThemeForest Quality team, before they’re approved for the page. That helps to pre-empt issues with outdated code, though the age of the theme and time since last update are still important factors. The August free themes have all been updated within the last 12 months, but one of them hasn’t been updated this calendar year.
Affiliates can absolutely promote these themes, linking to the landing page 
Just make sure you add your affiliate tracking code to the URL as normal, and you’ll receive the standard affiliate commission from any new customers that you refer to Envato Market if they make a purchase or deposit within 90 days of arriving via your link.
To @tommusrhodus’ point on more visibility for author profiles, we’ve also added Author Profile links to the author names on the landing page - that change went live in last Friday’s update.