Not sure how it's now, but it used to be that you were not allowed to use Office from Bizspark for tasks other than development for Office. You were not allowed to run your office on Bizspark's MS Office so to speak, but you could for instance develop a plugin for Excel.
If you have a reference that says it's different now, let me know!
"It used to be that you were not allowed to use Office from Bizspark for tasks other than development for Office"
The BizSpark EULA has interesting wording which is a bit less extreme than what you are stating (this may have changed in the past few years; i'm pulling from July 2012 EULA):
"You may only install and use copies of the following Desktop Application and Desktop Operating System portions of the Program Software solely to design, develop, test and demonstrate your programs. [list includes the office suites]"
This lets you use Office in contexts other than pure Office development. As an example, for an analytics startup you can run your business in Excel to test against your platform. I use Excel in this way (it's easy to throw up an excel baseline for lots of tasks and compare it to my code).
For those that can't see it (i realize its an XLSX):
The "Visual Studio Ultimate with MSDN Subscription" is included as part of BizSpark membership at no cost (you don't even need to give a credit card -- although you do in order to use the free Azure benefits)
Office Professional Plus 2010, Office for Mac 2011 Home and Business, and Office 2013 are provided (the 2013 betas have been available for months).
For those wondering why Microsoft is doing this (they also include windows, visual studio and a boatload of other products) I suspect they are trying to get startups to use Microsoft software now so that they'll be paying users when they grow beyond the limits (something like 3M revenue) of the program.
Note that it does not include Office for Mac, at least the last time I looked in the downloads library (4 months ago or so). Edited to add: the linked spreadsheet says I'm wrong, so I'll log in and check.
If you have a reference that says it's different now, let me know!