This is just a note regarding the requirement for input forms to behave in recognised way, and allow the form to be submitted by using the enter/return key, in addition to using the submit form button.
In the ops-users mailing list, this issue has been discussed.
http://mail-archive.objectweb.org/ops-users/2006-07/msg00237.html
As described, the behaviour has been added to a more recent version of the orbeon software.
In the meantime, there is a work around by adding the following element to an input field so that on clicking enter/return the form will be submitted:
<xforms:send submission="main" ev:event="xforms-value-changed"/>
This will submit the form in response to: a change to an instance data node bound to a form control e.g. when a value has been entered in the input field and the return/enter key used.
The login input form has been updated and the element above added to the password input field.
Other input forms will be updated accordingly if it is identified to be beneficial to the user interaction.
This behaviour as default will be available following an upgrade of the ops software. It is my view at the moment that an official release from orbeon should be used before upgrading the software, and not the interim builds.