MSX is the name of a standardized home computer architecture, first announced by Microsoft on June 16, 1983. It was conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation. It is said that Microsoft led the project as an attempt to create unified standards among hardware makers.
Despite Microsoft's involvement, the MSX-based machines were seldom released in the United States, but were popular in Asian countries like Japan and South Korea, South American countries like Brazil and Chile, and in the European market in countries like the Netherlands, France, Spain and Finland. To a lesser extent, the MSX platform was also popular in the former Soviet Union and Kuwait.
Before the appearance and great success of Nintendo's Family Computer, MSX was the platform for which major Japanese game studios, such as Konami and Hudson Soft, produced video game titles. The Metal Gear series, for example, was originally written for MSX hardware.
CocoaMSX is an open source MSX emulator, based on blueMSX, one of the most accurate MSX emulators currently available, with built-in support for 3 virtual systems, automatic download and installation of over 200 MSX systems. You can find all info on pokebyte's github page, and download from here.
fMSX was one of the first MSX emulators to be released, and over the years it has developed into one of the best. In accordance with the wishes of the original author, Marat Fayzullin, this OS X version is shareware software, with a registration fee of $20. I don't see any restrictions with non registered version. You can download fMSX from Richard Bannister's site.
openMSX is an emulator for the MSX home computer system. Its goal is to emulate all aspects of the MSX with 100% accuracy: perfection in emulation. You can find everything you ever wanted to know about MSX, and more, in the Ultimate MSX FAQ.You can download openMSX from it's homepage download area.