These people are having a good time.
Some people are enjoying themselves.
These people are some people. Having a good time can be more vaguely described as enjoying oneself.
exists e1 s1 x1 x2.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & n_time(x2) & a_good(s1) & Theme(s1,x2))
exists e1 x1 x2.(n_group(x2) & Theme(e1,x2) & Actor(e1,x1) & v_enjoy(e1) & n_people(x1))