I just want to clairify a little here...

This could still be a issue for commercial module sales. There are cases of single installs with a object qualifier on them in the wild. Even if you think now this will always be a in house module It still gives flexibility down the road to work in all situations if they change.

Simply put, use:

http://dnnlinqtosqladapter.codeplex.com/

and you can use Linq to SQL with DotNetNuke without any issues.

Note that Mitchel's comment was written before I released the LINQ to SQL model adapter; though his opinion about its overall utility may not have changed, the objectQualifier/databaseOwner consideration is largely assuaged.

That said, ORM technology has improved over the last few years to the point where it is likely to be viewed as a preferred-practice by a majority audience.  While I am relatively agnostic about the particular technology choice that is made (L2S, EF, Hibernate, et cetera), I would expect more and more module developers to be moving in this direction.

Brandon

(Coincidentally, I released a similar set of adapters targeted at the Entity Framework yesterday which, in a manner similar to my L2S adapters, allows runtime-adaptation of a DotNetNuke installation's objectQualifier and databaseOwner.)