  Automated summary quality assessment falls into two categories:
reference-based and reference-free. Reference-based metrics, historically
deemed more accurate due to the additional information provided by
human-written references, are limited by their reliance on human input. In this
paper, we hypothesize that the comparison methodologies used by some
reference-based metrics to evaluate a system summary against its corresponding
reference can be effectively adapted to assess it against its source document,
thereby transforming these metrics into reference-free ones. Experimental
results support this hypothesis. After being repurposed reference-freely, the
zero-shot BERTScore using the pretrained DeBERTa-large-MNLI model of <0.5B
parameters consistently outperforms its original reference-based version across
various aspects on the SummEval and Newsroom datasets. It also excels in
comparison to most existing reference-free metrics and closely competes with
zero-shot summary evaluators based on GPT-3.5.
