'Poz' is a colloquial term that refers to people living with HIV (PLHIV). It is common in a number of English-speaking countries. Peer-based PLHIV organisations, especially, use it a lot.
It is a play on words that comes from 2 meanings of the word 'positive' in English:
If something is positive, it is good, constructive, optimistic, confident, desirable A person who is “HIV positive” is a person who has HIV
So, when we use 'Poz' to talk about PLHIV, we mean it in the spirit of empowerment and self-determination.
QoL is short for 'quality of life'
So, overall, PozQoL means good quality of life for people living with HIV.