Yes, there are a lot of "addons" that are not available. But you can bet, that they will be.

I'm an ex phpnuker and ex postnuker ex phpwebsite! (Ever heard of SuperBB?
SuperBB Yup, that's me. I was using phpnuke, then postnuke, and wanted to integrate a forum called WebBBS. I was successful, but I needed a php script to do it better, so I took the Cyboards, a very viable script and integrated it to nuke, then I was going to get some help and we started the SuperBB project. It didn't get far. Too many chiefs and not enough indians, pardon the pun, at postnuke. Want to write mods for the nukes? Hope you got time to make a million changes to your scripts.

Toooo much work to keep your script working with their upgrades that are supposed to be better. Don't get me wrong, they are great scripts, but if you want a good forum for your site, go with UBBThreads and write your mods or addons (or get them here, or hire someone

for UBBThreads. It will make upgrading a LOT easier!!!)
Pick up a book on php, a recomendation would be PHP and MYSQL Development, and Sams Teach Yourself PHP in 24 Hours. Of course, it takes trial and error, but you can write your own modules if you really want to take the time. Or, you can come here and learn, or even more hire someone.
Obviously, this is only my humble opinion. They were good scripts when there was good direction. I tried it, scripted with it, had a bad experience with it, got fed up with it. I wish you good luck with the nukes.