Will my custom-made extension be added to the OpenCart Marketplace?

In most cases yes. This is because more than likely there will be other persons who are interested in having the functionality provided by the custom-made extension on their website. If you do not want your custom-made extension to appear in the OpenCart Marketplace, you will have to pay more for it than you would normally pay in the Marketplace. This is due to the fact that we would lose out on making extra money from the custom-made extension, so we would have to charge a premium price. Most clients do not have a problem with their custom-made extensions appearing in the Marketplace. Just be aware of the extra cost you would have to pay if you do not want to have your custom-made extension appearing in the OpenCart Marketplace.