Open Source approach in two metaOS projects. - Rosaria Rossini; Marco Jahn; Anastasios Zafeiropoulos; Nikos Filinis; Dimitrios Spatharakis; Ioannis Dimolitsas; Eleni Fotopoulou; Constantinos Vassilakis; Symeon Papavassiliou; Theodore B. Zahariadis; Ilias Nektarios Seitanidis; Enric Pages; et al. (MECC@EuroSys, 2025)