What are some alternatives?
When comparing Sell My App and Theme Forest, you can also consider the following products
Codester - The marketplace for ready-to-use web development assets
Elegant Themes - Simple, yet beautiful WordPress themes with easy to use implementation and support.
Creative Market - Buy and sell handcrafted, mousemade design content like vector patterns, icons, photoshop brushes, fonts and more at Creative Market.
SquareBit.io - A digital product marketplace with deep Git integration.
StudioPress - StudioPress offers superb WordPress themes with well designed site architecture to ensure search engine visibility along with unprecedented framework control.