Thanks for the help, I appreciate it.
I've tried giving the specific role contribute access to the project. Within the Advanced contribute settings I only turn on "Edit Custom Form", "Log Hours", and "Share". This DOES give the role the ability to edit the custom form, however it appears they can edit ALL custom forms on the project, and not just the single form that I'd like to make available to them.
Is it perhaps not that I need to enable access on the one custom form, but disable access on all the other forms?
Yea, I think in general, when you give contribute access to a project, they can edit all forms. I don't know if you can limit it on a per form basis or not. I've never tried to do it this way because I limit access to edit via form sections and not an entire form.
The way I would do it is to create a section on the standard project form that only certain roles, teams, etc. can edit but everyone can read it. I don't know your overall goal with custom data on a project but this approach has served me well for years. I only have one project form; with sections that are triggered by display rules and limited permissions to edit and/or view. The fewer forms, the better.