[eluser]OverZealous[/eluser]
I don't know the first thing about Django!
DataMapper is primarily (solely?) a ORM (Object-Relational Mapper), and it is only concerned with getting information in and out of the DataBase.
If I ever get my next big update out (and it will probably be a little while), I'll have the ability to extend DataMapper in a clearly specified and shareable manner. Then it might be possible to add something like a scaffold for those who want it.
The alternative would be to build a lightweight scaffold around DM. Someone else would have to do that, however. ;-P
I already use some custom tools to kinda do this, but here's some hints for someone who wants to try:
1) I include an additional element in my Validation rules called 'type', and I assign that a value like 'line', 'text', 'checkbox', 'select', etc. You could name this whatever you want. This helps generate the correct control.
2) I have a library that, when given a DM Object and field name, converts that field into HTML markup. (Mine is extremely specific, however, because I am relying on the Dojo JavaScript framework for client-side processing.) You should pay attention to certain rules, such as 'max_length' and use these to customize the form.
3) If you wanted to automate this, you would need too loop through the validation rules, and generate a HTML for each one ('id', of course, would become a hidden input).
4) The real problem comes from the relationships, which would be interesting to see someone solve in an automated manner.