HDSDR is described as 'freeware Software Defined Radio (SDR) program for Microsoft Windows 2000/XP/Vista/7/8/8.1/10. Typical applications are Radio listening, Ham Radio, SWL, Radio Astronomy, NDB-hunting and Spectrum analysis'. There are more than 10 alternatives to HDSDR for Linux, Windows, Mac and Android. The best alternative is Gqrx, which is both free and Open Source. Other great apps like HDSDR are CubicSDR (Free, Open Source), GNU Radio (Free, Open Source), SDR# (Free) and SDRangel (Free, Open Source).
Gqrx is a software defined radio receiver powered by the GNU Radio SDR framework and the Qt graphical toolkit. It supports many of the SDR hardware available, including Funcube Dongles, rtl-sdr, HackRF and USRP devices.
SDR# (SDRSharp) is a popular, simple, fast and extensible Software Defined Radio program written from scratch in C# to experiment new Digital Signal Processing techniques and push the Microsoft .NET Framework to its limits.
A graphical application for showing the Fast Fourier Transformation (FFT) as graph and waterfall diagram of the radio spectrum retrieved by Software Defined Radio (SDR) devices supported by GrOsmoSDR. Plugins enable demodulating a selected signal.
QRadioLink is a multimode SDR transceiver application using VOIP communication (radio over IP), built on top of GNU radio, which allows experimenting with software defined radio hardware using different digital and analog radio signals and a Qt5 UI.