HI.
To make this short and simple:
-My dad doesn't want me subscribing to TechNet for an unknown reason.
-I need to convince him to let me subscribe.
-It would save me ALOT of money considering how much Windows 7 Ultimate is, plus the other applications I can get with this subscription.
-He knows I'm into computers and he knows that I'm currently interested in programming(C#).
I'll be paying with my own money.
The subscription is $249.99 + tax because of a promo/coupon code. That price beats Windows 7 Ultimate(Full) BY FAR.
How can I convince my dad to let me subscribe WITH MY OWN MONEY to TechNet?
You might want to ask what the reason is he doesn't want you subscribing. I'd suspect it's not entirely "unknown," especially if you're looking to install Ultimate on "many computers" as you indicated elsewhere.
You certainly don't need all the features of Ultimate. It also doesn't sound like you're truly reasoning from an educational / evaluation perspective, but almost entirely from a financial one and without regard for the actual individual licensing purposes of things like Technet.
You (and your family) would almost certainly be just fine with one of the Home Premium upgrade family packs, and/or perhaps a copy of Professional. And that route is less expensive than what you'd seek and won't lead you into licensing issues, either.
If you truly want to learn your computer science, you don't need Ultimate / Technet for the kinds of things you'd need to be learning now. If you want features like BitLocker, now's the time to learn more about open source stuff like TrueCrypt, rather than simply using the mass-market basic stuff.
And if you're truly interested in educational-type things, you're in a situation where you'd be eligible for academic resources and discounts on things (including occasionally for Technet), and your time and resources would be much better spent looking into those and familiarizing yourself with how they work.
Look into the MSDNAA stuff which is more geared towards students and academic settings. The Technet stuff is generally more for IT professionals.
(And yes, you're indeed misunderstanding OEM licensing, too, as already described.)