The short answer is yes, if you are simply looking to split up the
options into multiple columns.
The long answer is: you'll need to create a new plasmature element
class, or modify the existing checkbox group plasmature type to
support multiple columns. (A plasmature element class represents a
kind of form element in Disco.)
Once a plasmature type exists for the particular form element you
want, you should be able to modify an element in a form view to use
that plasmature type.
That said, if you are looking to create an actual grid of checkbox
elements (not just simple columns), the Reason forms tool is probably
not sophisticated enough. You can still use Reason to do what you
want, but you'd need to develop a module, do more of your own db
plumbing and set up the disco form in code, using Disco and its
element groups feature, rather than setting up the form in the Reason
database.
Matt