I'm using this on vbulletin 4.1.9 and it works 100%
I'm so happy you, you don't know how much I appreciate this mod, it's a life saver for me
Marked as installed and nominated for mod of the month...
I've fully tested it and it's excellent... for the noobs like me to vbulletin, here's a simpler install explanation (no offence OP but I found your directions difficult to understand)
1.) download and extract all files
2.) upload the bitfield_allowhtml.xml (Open up the includes folder, then open the xml folder and you will see - bitfield_allowhtml.xml
3.) Now put this file into somewhere like /public_html/forum/includes/xml
(your file path may differ but basically put this file using FTP into the xml folder of your forum)
4.) Admin CP -> Plugins & Products-> Manage Products -> [Add/Import Product]
Now see "EITHER upload the XML file from your computer"
Click the button and upload the last file called "product-nzbgroupallowhtm"
Click import and your done. There is basically only 2 files to this entire install.
If anyone finds my directions too hard to understand then vbulletin isn't for you and I suggest outsourcing work like this. This is as easy as it gets!