Weka is open-source machine learning software issued under the GPL (ml.cms.waikato.ac.nz)

Weka is a long-standing, open-source machine learning toolkit distributed under the GNU General Public License (GPL). It bundles a broad collection of classic ML and data‑mining tools — classification, regression, clustering, association rule mining, feature selection, data preprocessing and visualization — accessible through a GUI, command line, and Java API. Weka uses the ARFF data format and an extensible package system, making it convenient for teaching, rapid experimentation and reproducible research workflows. For the AI/ML community the GPL release matters both practically and legally: researchers, educators and startups can freely use and modify Weka for prototyping and analysis, but derivative or redistributed software that incorporates Weka code must comply with GPL terms (i.e., remain open-source under a compatible license). Technically, Weka excels for classical ML pipelines and smaller-scale experiments rather than large-scale deep learning; its strengths are in algorithm variety, interpretability and an easy-to-use environment for benchmarking and feature engineering. The open-source, GPL-backed availability ensures continued community contributions, auditability of implementations, and a stable platform for comparing traditional ML methods.