I have been thinking about this for a while now. Linq to NHibernate requires two to three months of full time development work in order to get to a really good usable state. The problem is that we don't have anyone working on that full time. Considering the nature of OSS, this is not surprising, but I would like to change that if I can.
I am trying to getting sponsorship from several companies that are willing to pay for the development of Linq for NHibernate. The details are very simple, if I get enough companies interested in this to dedicate enough time & resources into it, we can get it working.
If you or your company are interested in helping fund the Linq for NHibernate project, please contact me privately, and we can discuss how we go about this.