Presumivelmente, eles fazem isso por razões técnicas, como todos os outros.
Aqui está a saída de grep -R Microsoft . | grep -i "(c)"
run na árvore de código 3.13.3:
./tools/hv/hv_vss_daemon.c: * Copyright (C) 2013, Microsoft, Inc.
./drivers/net/hyperv/hyperv_net.h: * Copyright (c) 2011, Microsoft Corporation.
./drivers/net/hyperv/rndis_filter.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/net/hyperv/netvsc.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/net/hyperv/netvsc_drv.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/scsi/storvsc_drv.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hid/hid-hyperv.c: * Copyright (c) 2010, Microsoft Corporation.
./drivers/video/hyperv_fb.c: * Copyright (c) 2012, Microsoft Corporation.
./drivers/input/serio/hyperv-keyboard.c: * Copyright (c) 2013, Microsoft Corporation.
./drivers/hv/hv_snapshot.c: * Copyright (C) 2013, Microsoft, Inc.
./drivers/hv/channel_mgmt.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/vmbus_drv.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/hv_util.c: * Copyright (c) 2010, Microsoft Corporation.
./drivers/hv/hv_balloon.c: * Copyright (c) 2012, Microsoft Corporation.
./drivers/hv/ring_buffer.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/hv.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/channel.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/connection.c: * Copyright (c) 2009, Microsoft Corporation.
./drivers/hv/hyperv_vmbus.h: * Copyright (c) 2011, Microsoft Corporation.
./Documentation/usb/linux-cdc-acm.inf:; Copyright (c) 2000 Microsoft Corporation
./Documentation/usb/linux.inf:; Copyright (c) Microsoft Corporation
./include/linux/hyperv.h: * Copyright (c) 2011, Microsoft Corporation.
A maioria deles tem a ver com suporte a hypervisor, como interfaces de rede virtual. Ou seja, de acordo com o artigo que você vinculou, eles ajudam a facilitar os convidados linux executados no hipervisor do Hyper-V da Microsoft. p>
Algumas podem também ser o caminho inverso - executar convidados do Windows em hosts linux - o que também é possível com pelo menos Xen .