Xtendify is described as 'Marketplace for Open Source CMS and Frameworks' and is an app in the business & commerce category. There are five alternatives to Xtendify for Online / Web-based and SaaS. The best alternative is CodeCanyon. It's not free, so if you're looking for a free alternative, you could try Codentheme or Noodlio. Other great apps like Xtendify are Alkanyx Marketplace and SugarKubes.