SFXsource is described as 'Provides professional royalty free sound effects and royalty free music to download for use in media productions' and is an app in the Audio & Music category. There are more than 10 alternatives to SFXsource for a variety of platforms, including Online / Web-based, iPhone, Android Tablet, iPad and SaaS. The best alternative is ccMixter, which is both free and Open Source. Other great apps like SFXsource are eoun.com (Free), YouTube Audio Library (Free), AudioJungle (Paid) and Premiumbeat.com (Paid).
AudioJungle is part of Envato Market. At AudioJungle you can buy and sell royalty-free music and sound effects that are completely Podsafe for just a few dollars, which includes a Buyer Fee. The site is home to a bustling community of audio composers and producers.