Some days ago I was asked about how to allow users to add forms to a forms library without having to grant users the Contributor role because with this permission level the users have also rights to change other's forms.   The answer is that the users only need Add and Read permission to add new forms to a Forms Library and the ability to read them.  What I forgot when I was giving my answer was how to create a permission level and add these rights to the new security schema.  The "quick recipe" about how to create a permission level will be:

1. Go to Site Action Menu.
2. On that menu, go to Site Settings.
3. Choose People and Groups
4. On the quick launch bar, there is a link to Site Permissions.
5. On the Settings menu, click over Permission Levels.
6. On the Permission Level page, you can click over new and create a new permission level.
7. Add the permission that you want (in this case, Add and Read).
8. Name it J
9. You can now use that permission level on your form library to allow users to create forms without having the risk of users modifying other people's forms.

This is an easy steps list, if you need more information about how to administer permission levels go to here.