Ernesto just finished a new document that explains a great way to integrate DBXL 2.4, qRules 2.4 and the SharePoint 2010 Sandbox for InfoPath browser forms:
http://www.infopathdev.com/files/folders/qrules/entry62469.aspx
Because of the new sandbox in SharePoint 2010 forms with code behind (in this case qRules) can be as easily integrated with DBXL as forms without code.
NOTE: if you are using SharePoint 2007 please be sure to take a look at this document that explain another way you can use qRules to integrate easily with IPFS and DBXL.
Ted