HELOCs are hybrid loans, they are secured by the property and a personal guarantee. As such, the lender has an option in default to either seek the property through foreclosure or seek a judgment from you personally. it appears from what you've stated that they are seeking the latter.
Lenders can do this and are increasingly doing so as a result of the downturn of the market. You should seek the counsel of an attorney licensed in your state, however, your general options are to either file for bankruptcy (assuming you qualify to do so) or negotiate with the lender.
The summons means that are you being sued by your lender for a default of your HELOC liabilities on the personal guarantee you made when signing the documents.
As a general rule if the judgment is issued against you, then you are liable for the debt, however it might be possible for the judgment to attach "joint" assets (i.e. bank accounts, other property etc...)
I would see an attorney immediately and decide how to move forward! Good luck to you!
Disclaimer: attorney's response is not intended as legal advice and is for informational purposes only. Inquirer should seek the counsel of a duly licensed attorney within that jurisdiction.