Hi,
Thanks for finding Qdabra!
qRules won't be the solution for you but DBXL might be. We have a free trial of DBXL available on Qdabra.com and we have free DBXL training modules and videos available here:
http://www.infopathdev.com/files/folders/dbxl/default.aspx
DBXL will allow you to submit your form's data to SQL and a SharePoint form library. If your legacy software is only querying SQL for data (not writing) then DBXL should be an appropriate solution. The free trial will give you the chance to try out the product and decide whether it will address your requirements.
If you'd prefer 1-on-1 assistance to get your scenario up and running quickly, Qdabra offers Consulting services and Support. Let us know how we can help. Thanks!