This is pretty standard stuff for most of the software giants. They spend a ton of money and time to develop and manage their products and for the most part it's all about combating rampant piracy. So, if you obey common laws regarding the use of Autodesk software for commercial or educational use, there will never be a day that they come knocking at your door. Autodesk has the most generous, awesome educational program where you can buy the full suite for pennies in order to learn and teach, and it's only right that you upgrade to the commercial version when you go on to "pro-work" that involves Maya.
True, Blender is free and open source which makes it super cool for many users on all levels, but unfortunately, software companies, just like most companies selling anything, will never be able to give their product away for free. Autodesk's EULA is simply asking it's users not to steal their software, it's as simple as that. Not to mention that Autodesk is a company with excellent customer support, cutting edge innovations, and stellar (for the most part) documentation on how to use their stuff. The price paid is worth every penny.