Rule 12. Using the work of others.
If you are developing something that is based on the work of another Member, you MUST first seek their permission and you must give credit to the member whose work you used. If a dispute occurs about who developed / created a piece of work, first try to settle the matter by private message and NOT in open forum. If this fails, you may then contact a Moderator and provide clear evidence that the work was created by you.
Convincing evidence will result in the copied work being removed. If there is no clear evidence that it was you who created the work, then in the spirit of sharing, all work will remain posted on the forums.
As an addition, developers have the right to hold exclusivity over their work for as long as it is deemed necessary by that developer. However, if the work is claimed as exclusive, it must remain as such. No selective sharing will be allowed (ie, allowing certain people to use it and not others). Should the developer decide to start sharing the work with others, the work automatically becomes fair game for all to use, albeit with the relative credit displayed.
In regard to permissions, the same rules apply for this but if permission was already given and unless there is a very valid reason, it cannot be revoked (same applies to major updates on the work). Under that same premise, permissions cannot be denied unless the work is exclusive or under extreme circumstances.
In plain English: If you want to keep your work exclusive, go for it. However, if you are going to share your work, do it fairly.
These rules apply to all software posted on XDA (including but not limited to ROMs, RUUs, apps, games, kernels, themes, icons, etc) unless that software comes with a license that waives these rules.