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SiPHome's Callbackbutton software requires a valid VoIP account, which is free. Users are recommended to choose the "Classic Prepaid" tariff, which doesn't have basic charges and comes with starting assets.

BackTrack is a live-CD Linux distribution that offers a selection of hacking and cracking tools. It stands apart from similar distributions with its wide range of features and free of charge.

Phoner is a free SIP-based softphone that incorporates advanced features from eyeBeam 1.5, a carrier grade telephony client. It is the market leader in VoIP software, and enables seamless communication with its advanced architecture, delivering a feature-rich user experience.

SiPHome offers a free Callbackbutton that requires a valid VoIP account. The recommended tariff is "Classic Prepaid" which has no basic charges and is also free. Additionally, it comes with starting assets.