Penny's OS 2.0 (S 13)

 

or MacBSD or MACE 
or Mach or MachTen 

or MacMach or Mach386 

or Mac OS or Mac OS X

or Madrid Linux or Maemo
or Magic Cap or Magic Linux
or magnussoft ZETA or MAI Basic Four
or Mandrake Linux or Mandriva Linux
or Mangaka Linux or Manhattan OS
or MANOS or ManRiX
or MarBSD or MaRTE OS
or Maruti or MaryanLinux
or Masix or MASTER
or Maverick OS or MAX 

or MaxOS or Mayix 

or MazzanettoOS or MBOS/5 

or MCNLive or MCP 

or MCS or MCTS
or MDOS or MDX
or Mediainlinux or MeDOS

or Medusa or Medya
or MeeGo or MegaOS
or Meglos or MeikOS
or MeNTOPPIX or MenuetOS
or MEPIS or Merlin
or MERT or Metadistro-Pequelin
or M44/44X or MFT
or Michigan Terminal System or Micrium
or MicroBSD or MicroC/OS-II
or Microdisk Op Sys or MICRODOS

or Micronix or Micro OS X 

or Microport UNIX or Micropower Pascal

or MICROS or MicroVMS
or Microwave OS-9 or MidnightBSD
or Midori or MikeOS
or MIKO GNYO/Linux

or Mimos or miniBSD 

or MINI-EXEC or MiniKazit 

or MINIMOP or Minirighi 

or Minislack or MINI-UNIX 

or MINIX or MiNT 

or MINUX or MIPS RISC/os

or Miracle Linux or Miraculix
or MIRAGE or Miranda OS
or miray unOS or MirOS BSD
or MIT Exokernel or MiX

or MiZI Linux or MK-DOS 

or MkLinux or MK++
or mkRTOS or ML 

or MMOS or Mobilinux

or Möbius or Moblin
or Mockup or MOD4
or MOD-400 or MODULAR ONE
or ModulOS  or MODUS4
or MoLinux or Momonga
or MonaOS or MONECS
or Monitor or Monoppix
or m0n0wall or Monta Vista Linux

or Monterey or MoonOS 

or MOPSLinux or more/BSD

or Morphix or MorphOS
or Mort or MOS
or MOSIX or MOSS
or Mostly Linux or MotoMagx
or MoviX or MPE/iX
or MPE-3000 or MPE/XL
or MP/M or MP/M-86
or MP/NET or MPOS

or MP/OS or MP-RAS UNIX

or MPX or MPX-32
or MQX RTOS or MrCODE
or MSC or MS-DOS
or MS/8 or MSOS
or MSP or MSP/7

or MST UNIX or MSX 

or MSX-DOS or MTDS 

or MT-809 or MTK-II 

or MTOS or MTS 

or mtxinu or MU5 

or Mulimidix or muLinux 

or Mulplix or Multics 

or Multi Distro or MULTIDOS 

or MULTI-FORTH or MultiJob 

or Multi-Programming Executive or Multiuser DOS 

or MUMPS or Mungi 

or MUNIX or Munjoy Linux

or MuOS or Muriqui Linux
or Murix Linux or MUSIC
or Musix GNU/Linux or MUSS
or MustiOS or Mutagenix
or MUTOS 1700 or muVinix

or MVS or MVS/ESA
or MVS/SE or MVS/SP
or MVS/XA or MVT

or MV/UX or Myah OS 

or MyDOS or myLinux 

or MyNOS or MysticOS
or Mythbuntu or MythDora