Some Microsoft software was supported on other Unix platforms through Wabi and similar tools, and IIRC there may also have been native ports. Microsoft rather pointedly has avoided supporting the Linux market, with the exception of tools which allow interoperability with Windows systems (notably kernel contributions most of which relate to Azure).
> Microsoft rather pointedly has avoided supporting the Linux market.
Please. Wake up and smell the coffee.
EVERY major software company has avoided the Linux market. It's because of the questionable market opportunity that is the reason not any competition issues.
As noted: there was specific end-user software supported on Unix platforms, which could be, but never was, trivially ported to Linux.
More tellingly: Linux's overarching success has been in the server space (and the platform is emerging as the mobile leader). Microsoft's server software, including most notably SQL Server (derived from Sybase, originally targeted at Unix systems) isn't available for Linux. Neither are Exchange, Active Directory, Sharepoint, IIS, or Windows File Sharing. Free Software (and proprietary) alternatives and work-alikes for each exist, and in many or most cases are more successful, though AD remains a market leader.
Microsoft conquered the desktop PC market by leveraging compulsory per-CPU OS license via bundled office software to create a self-reinforcing illegal monopoly, which it then attempted to extend into the small server space. It's fought every attempt to crack any part of that stranglehold, fighting OEMs providing other operating systems (DR DOS, Novell, BeOS, Linux), by not porting its Office products (except to Mac OS X, since discontinued), and by not porting/building its server products to other platforms.
Major companies which have not avoided the Linux market include IBM, Oracle (and acquired companies Sun and PeopleWare), and Informix. Yes, all server space. I'm making a point here.
