Using them in commercial projects without a receipt from the foundry can lead to legal liability. Incomplete:
Protonema Regular Font — Free Download Protonema Regular Font Free Download
Protonema Regular is a visually appealing geometric sans-serif available for free download, but only for personal, non-commercial use unless explicitly stated otherwise. For commercial projects, a paid license is likely required. Always verify the license file before use. Using them in commercial projects without a receipt