While there is a Forms Add-On available through our Professional Service's team, if you are restricting your user from posting to discussions, I do not think this would work for your use case. However, if you are interested in developing a custom solution for your instance there are a few options:
1. If you would like assistance developing a custom add-on for your instance our Professional Service's team can work with you to determine the scope of the project and assist in developing a custom solution which meets your needs. If you are interested in this option please submit a case in your customer group, here in the Jive Community, and the next available support engineer can get an engagement started for you.
2. If you are interested in developing a solution yourself I would recommend checking out the Jive Developers space here in the Jive Community where you can collaborate with other developers on custom implementations they have made in their Jive instances.