Minecraft cracked to premium LAN connection?

So I bought Minecraft premium (transitioned from Mineshafter), but my friends haven't. Before buying MC we played on a LAN world using hamachi and everything worked fine, but now when I try to set up a LAN world where I can play with my friends, they can't seem to connect. I tried using my Mineshafter client but it's the same issue. I tried logging in on Mineshafter with a different username, but still no dice. I also got one of my friends to set up a world on their Mineshafter client and I tried logging in, but it didn't work; I kept getting this Java script error thing. I know that we're all using the same version of MC (1.7.2) and that we have a direct tunnel (green dot) on hamachi, but nothing seems to work. Is there any way to fix this problem other than having my friends buy MC premium?

Thanks in advance!

Added (1). I'm not using any server programs like Bukkit or anything. I simply create a single player world and use the 'Open to LAN' option in the menu and then I send my IP address and assigned port to my friends.

Have you opened your ports? Try going to your server folder and server properties config file then write False in that line I can't remember what it is called, but it has to do with your connection… Gah.