You don't have any duties or obligation towards any individual to assist them with their issues.
The only obligations you have is to be honest about the project. For example, if you know that the project is not written with security in mind, you must announce the fact, so that people don't go using the project assuming you took care of all potential exploits.
Beyond that, you have no obligations towards anyone. Quite the opposite. You've already done your part. You donated the product of your effort for free. The obligation is on people who use your product. If they want you to care of their issues, they are obliged to give something back in return. At the very least, appreciation.