‘Bronze’ open access supersedes green and gold

Most open-access articles are not accompanied by a license, severely curtailing their use, a recent survey of 100,000 articles sampled from the CrossRef database has revealed.

Without a license, articles are free to read, but can’t be redistributed or reused, for example, in presentations or course material, says Heather Piwowar, co-founder of the open science not-for-profit ImpactStory, who led the analysis. Without explicit permission, they also can't be mined by computer software. “As artificial intelligence and machine learning become increasingly important tools, we need our research literature open and available for computational approaches to synthesize it, summarize it, and discover new patterns,” she says.