UBB.threads PHP Forum Software Community Forums UBB.threads Version 7/8 Support how to display forms for guest users

Or do you mean that you want guests to be able to read threads but not post?

You need to enable guest access by entering 1 in the Guest options here:

CP > Forum Permissions > Can See Forum > Guest [1]
CP > Forum Permissions > Can Read Topics > Guest [1]

Work through the options and anything that you don't want guests to have access to enter 0.