Yes, but don't expect to earn much. This forum is filled with threads about how forums don't perform well on Adsense due to audience indifference to ads.
Yeps diamond is rite they perform poorly, unless u put a large rectangle right after the first post, then u get a pretty good ctr ;)
I second that it is allowed. I even complained to Google about poor targetting, and they actually sent me a relevent reply. So they know about it, and have a helpful form letter for problem-solving.
I also second that there are no big bucks to be made.
This forum thread is about something who thinks their Google adsense account was cancelled because he runs a forum:
There is no downside to adding AdSense to a forum. Anything you make is 100% profit, so do it. I have it on a large forum and it makes money.
Can you just tell how many visitors (posts) per day and how much does it bring? At least approx values. Thanks a lot.
I run Google AdSense on a (phpBB) forum of mine; and have also written a non-public hack to allow the Google AdSense spider into some of the private forums.
My posting at [webmasterworld.com...] gives some helpful tips on how to get AdSense working better for you, and this is especially relevant with phpBB, which isn't written very well for search engines and spiders to go through.
It's important that a thread about, say, mobile phone costs are accompanies by mobile phone ads, and a thread about how to boil a chicken gets accompanied by chicken boiler ads: to achieve this, you essentially need to re-write most of the phpBB templates to make them easier for the spider. This is a lot of work.
One thing I have done is obfuscate the mention of "phpBB" in the forums; both to 'hide' my phpBB forums from recent worms, but also to stop ads for phpBB hosting appearing, which were inappropriate to the subject matter.
I've also placed an ad placement position WITHIN the forum posts, so that they're in the content that people read. (Again, this is a non-public hack I've written). This does better in terms of click-thru, especially if the content is relevant to the subject matter.
Hope that's helpful.
Listen to James he said everything I have learned as well. James did you fix the next /previous post problem in phpbb? I changed my to redirect the request to the right thread instead of just printing out the next thread. really heled reduce my "duplicate content"
I've not done that: good idea. It's the 'latest post' link I have most problems with, because I'll rarely - if ever - have contextual ads on those page addresses since they change so often.
I've also changed all the page names from .php to something else (an abbreviation of my site name, actually) so that the worms won't realise it's phpBB any more - but that's got nothing to do with AdSense.
(Although - actually - if it was changed from viewtopic.php to viewtopic.widget I wonder if it would get more ads relevant to widgets? Hmm.)
I am using mod_rewrite to make it all have a .html extension. Sent my indexed pages through the roof. I had to put a spider logger in there to turn off session ids though for the spiders.