Question

what is the difference between positive and humanistic psychology

Answer 1

Very nice question!
These two paradigms of psychology often get misused and confused so in my opinion this question should be a sticky :P Anyway, the difference is mainly (as with all paradigms) what is being focused by them (1) and as a reaction to what they have emerged (2).
Just like gestalt-ism got being into existence because of structuralism (basically denying that the psyche is the sum of the parts composing it), behaviorism exists because of psychoanalysis (there is no subconscious because you can't measure it).
As such humanistic psychology is a paradigm born in the mid 20th century as a reaction to behaviorism (no its not that mechanical!, said the humanistic Maslow, Rogers etc.; the human wants to AUTO-ACTUALIZE himself. Not just responding to external stimuli. It has internal needs!) This direction of research gave us the Motivational Pyramid, Self-focused therapy and a lot of interesting theories on many aspects of the human mind. the web is full of material if you need more on this. Just google it :)
On the other hand, positive psychology is late 20th century psychology branch that developed as a reaction to psychiatry and anti-psychiatry that battled what is a sick person and what is not making psychology more a science of the sick then a science of the mind in general. "Positive psychologists seek to find and nurture genius and talent, and to make normal life more fulfilling" (Wikipedia) said Mihaly Csikszentmihalyi (pronounced "Me - ha - y Cheek - sent - Me - ha - y") the father of positive psychology.
Hope this helped, good luck on your journey finding more info.
Cheers!