UniversalCEFR: Enabling Open Multilingual Research on Language Proficiency Assessment. - Joseph Marvin Imperial; Abdullah Barayan; Regina Stodden; Rodrigo Wilkens; Ricardo Muñoz Sánchez; Lingyun Gao; Melissa Torgbi; Dawn Knight; Gail Forey; Reka R. Jablonkai; Ekaterina Kochmar; Robert Reynolds 001; et al. (CoRR, 2025)