Hi,

While the reply from Baijiu is 100% correct and a great answer I would love to add some more information on this.
You can indeed sell the module on Odoo and get paid for it (70%) through https://apps.odoo.com/apps/upload/ but there is a second catch.
Odoo is licensed under the AGPL license (for V8, this will change in V9) and this means that the AGPL license does not forbid requiring payment for the distribution of AGPL covered software however the full terms of the License continue to apply, which means that you must provide the source code along with the software, and that anyone who receives it may freely modify or redistribute it under the terms of the AGPL

As quoted from Ray Carnes (https://www.odoo.com/nl_NL/forum/help-1/question/can-i-sell-an-odoo-module-53562)

The AGPL license does not forbid requiring payment for the distribution of AGPL covered software, however the full terms of the License continue to apply, which means that you must provide the source code along with the software, and that anyone who receives it may freely modify or redistribute it under the terms of the AGPL. For example, you cannot ask people who receive your modules not to re-distribute it, they may do so freely. 

Note: Keep in mind that selling copies of an Odoo Module is distribution, so this is not compatible with the "Private Use" exception granted by Odoo Enterprise.  Any modules written as '"Private Use"cannot be distributed.

In other words, since any module is a derivative work of an AGPL software product, the AGPL license applies to all modules - so the first person to buy your module can legally distribute it to anyone else - and you cannot legally prohibit this.

If you encounter any company selling Odoo modules, be sure they respect the license and understand this.  Companies that sell 'support'and 'services' related to modules are more successful that thoes that sell modules.

In Odoo V9 they will change from AGPLv3 to LGPLv3, which means there are more options for you to sell and distribute your app. There is a great topic about this here: https://www.odoo.com/nl_NL/forum/help-1/question/why-is-odoo-changing-their-license-from-agplv3-to-lgplv3-for-version-9-0-75453

Quoted from Stephen:

 Odoo announced that they will be changing their license for Odoo v9 fromAGPLv3 to LGPLv3.  The main difference is that now module developers do not have to provide source code for their modules to their customers allowing developers to have more control over their intellectual property.  (see Google doc for all of the changes).

These changes are schedule for Odoo v9 as long as Odoo can get all code contributors to agree to the change (2% of Odoo base code has been written by the Odoo Community).

Hi,

You can submit your apps in this link :- https://apps.odoo.com/apps/upload/

you need to signed-in in your ODOO account to do this,, follow the instructions there.

Want to sell your own module ?

It is possible to sell your own module on our platform. You will get 70% of your modules revenues each month. To sell a module, you just have to add a price key in your module manifest like 'price': 49.99, for example. The price is expressed in EUR by default, but you can also express it in USD by adding 'currency': 'USD', to the manifest.

Hope this helps....