It depends a bit on your usecase, but there are several ideas for you.
Since "Terms of Use" can be a webcontent, you can place any
content there. You could insert a javascript "application"
into the terms of use page that way that allows you to control the
process. You could communicate with the backend using rest services
and update data from there.
Another idea would be to use a post login hook to redirect the user
to a page after login. And there you can place any application you
want. Of course, since it is only a one time redirect after login,
users could simply ignore the form and go to another page. But that
could be fine for you.
https://help.liferay.com/hc/en-us/articles/360018151311-Performing-a-Custom-Action
Another idea would be to use a filter. That filter could check all
requests and act similarly to the terms of use filter, when some
conditions are met, present the user with a form.
https://help.liferay.com/hc/en-us/articles/360020486752-Servlet-Filters
Or you could add something to the theme. Then a user could be shown
the form instead of the regular page content on every page.
