If you mean "have to" in the sense of "if you buy a N810WE you are automatically signing up for a service fee"? If it's anything like the GPS service on the N810 (nonWE) (almost pronounces like enui), then no. If you don't want to have WiMAX, and just want a black&amber N810, then you probably wont have to activate the WiMAX service and can use it just like the N810 (nonWE).

If you mean "have to" in the sense of "does WiMAX service cost money, or is it free with my N810WE"? ... I'm quite certain that Sprint doesn't offer XOHM on a charity or non-profit basis. So, yes, you'll have to pay for it in some fashion. :-)