The only thing that ran out is the Support which you get via ticket, and the forums, and missing out on any new versions of IPB. Also if you've never used IPB it would be best to renew and get the support.
And for some reason you will need to renew the license to download IPB anyways as i don't have a copy saved on my computer to pass over.
Edit: Dont buy from Digtal point unless you like being scammed.
Honestly, I would do it properly and buy a full license. Why? Licenses aren't actually transferable. Obviously you can change the details on the license etc, but it's messy. Given that it's the internet, I would be very wary of entering any sort of financial deal, especially of that sort.
Buy a license from the IPS and you're completely secure. It's $150 I know, but it also is the best software currently available on the market. If you want to continue running forums over the next five or six years, then it's a worthwhile investment.
Also, you don't need to renew your license every six months unless you absolutely want upgrades every six months. I've dodged renewals for up to four months at a time. The IPB company forums will give you advice if you have a problem anyway, you just can't send tickets.