I am creating a Drupal commerce Payment module and planning to sell it through codecanyon. Is there any licencing issues if I proceed with this?
Any module you distribute must be licensed under the GPL 2.0 or later. You are free to put it up for sale so long as anyone who buys it enjoys the same rights of redistribution - that's just the nature of Drupal's license overall. Anyone who buys your module will be free to put it up on drupal.org and redistribute it at will.