  Open source software (OSS) licenses regulate the conditions under which users
can reuse, modify, and distribute the software legally. However, there exist
various OSS licenses in the community, written in a formal language, which are
typically long and complicated to understand. In this paper, we conducted a
661-participants online survey to investigate the perspectives and practices of
developers towards OSS licenses. The user study revealed an indeed need for an
automated tool to facilitate license understanding. Motivated by the user study
and the fast growth of licenses in the community, we propose the first study
towards automated license summarization. Specifically, we released the first
high quality text summarization dataset and designed two tasks, i.e., license
text summarization (LTS), aiming at generating a relatively short summary for
an arbitrary license, and license term classification (LTC), focusing on the
attitude inference towards a predefined set of key license terms (e.g.,
Distribute). Aiming at the two tasks, we present LiSum, a multi-task learning
method to help developers overcome the obstacles of understanding OSS licenses.
Comprehensive experiments demonstrated that the proposed jointly training
objective boosted the performance on both tasks, surpassing state-of-the-art
baselines with gains of at least 5 points w.r.t. F1 scores of four
summarization metrics and achieving 95.13% micro average F1 score for
classification simultaneously. We released all the datasets, the replication
package, and the questionnaires for the community.
