Retro Virtual Machine is described as '(or RVM for short) works natively in MacOs (from version Mavericks 10.9), Linux (any modern distribution) and in Microsoft Windows (from Windows Vista)' and is an app in the Gaming Software category. There are five alternatives to Retro Virtual Machine for a variety of platforms, including Windows, Linux, Online / Web-based, Android and Self-Hosted solutions. The best alternative is Fuse, which is both free and Open Source. Other great apps like Retro Virtual Machine are Speccy emulator (Free), JSSpeccy (Free, Open Source), Qaop (Free) and Spectaculator (Freemium).
Fuse (the Free Unix Spectrum Emulator) was originally, and somewhat unsurprisingly, a ZX Spectrum emulator for Unix. However, it has now also been ported to Mac OS X, which may or may not count as a Unix variant depending on your advocacy position.
Speccy is a cross-platform emulator for Sinclair ZX Spectrum. FEATURES - Emulates 16kB, 48kB, and 128kB versions of Sinclair ZX Spectrum, Spectrum +2, +2A, and +3, and Timex Sinclair models. - Supports all types of ZX Spectrum joysticks and the Kempston mouse.