The latest release of Vbulletin has support for Adsense integration, however there are a number of limitations, so I'd recommend you read this thread:
How to Integrate Google Adsense in 3.8 - vBulletin Community Forum
Key points:
- you can only use one publisher ID with your vbulletin account
- you need to link your vbulletin account with your adsense account before you can access the new features
How to Integrate Google Adsense in 3.8 - vBulletin Community Forum
Key points:
- you can only use one publisher ID with your vbulletin account
- you need to link your vbulletin account with your adsense account before you can access the new features