You wish to access cloud applications such as Microsoft Office 365 from a Windows Embedded Standard 2009/7 or Windows Embedded XP device.

Microsoft's Additional Terms for Runtime Licenses for Windows XP Embedded and Windows Embedded Standard 2009/7 state in ยง34 (Cloud Computing Devices):

Company may allow an Embedded System to use Internet browsing functionality to connect to and access cloud hosted applications (for example, Microsoft Office 365), provided that:

(a) Company shall not allow any Desktop Functions to run locally on the Embedded System;

(b) Any files that result from the use of Desktop Functions must not be permanently stored on the Embedded System; [...]

This means if you have a Microsoft Office 365 Business Plan such as Office 365 Business Essentials or Office 365 Enterprise E1 (both providing the "Online versions of Office including Word, Excel and PowerPoint" functionality) you may use an IGEL Windows Embedded device (UD3, UD5, UD6, UD9 or UD10) to connect to Microsoft Office 365.

IGEL does not provide any Microsoft Office 365 plans, packages or promotion bundles!

Windows Embedded licences do not allow installing applications such as Microsoft Office locally on the device.

This does not apply to Windows 10 IoT.