Trusted QSL keeps eQSL an open and free activity for amateur radio operators. It promotes the Digital Signature Standard (DSS).
Fldigi is a digital modem application for common amateur radio systems. It supports CW, PSK, MFSK, RTTY, Hell, DominoEX, Olivia, and Throb. It also helps calibrating a sound card to a time signal and perform frequency measurement tests. Flmsg is a messaging tool over digital radio, while Flarq supports ARQ file transfers.