I have been granted permission to reduce the rules from our custom license used in Advanced Electron Forum project. I am not sure what exactly is needed to make the license above an open source license for the product but I think that third term is the one that should be removed/changed.
Yes, point 3 has to go, and as I understand it, so does point 6, since a true open-source license has to be "non-discriminatory," and what's illegal in one country may not be in another.
But if you really want to make the work widely available, why not just use an existing open-source license? Take a look at the Mozilla Public License if you want the open-source nature of the code to be protected, or the BSD or MIT licenses if you don't care and only want to get people to use the code itself.
Sounds like what you are looking for is something like the Common Public Attribution License which is known as a Badgeware license. It did get OSI approved but it's not going to be particularly popular. The only issue is the copyright notice displayed on startup vs bottom of a page and how it applies to websites (should be ok as it's listed as being applied on the graphical user interface), the worst that happens is someone goes to lengths to have the copyright notice disappear after the first page visit. There is also the Adaptive Public License.
The original 4-clause BSD license has an clause requiring advertising.
Most commercial opensource products normally work by dual licensing under a GPL/commercial license. They keep a 'pro' version that has more features, better performance and so on but that doesn't seem like it's feasible for your situation.
It's worth thinking about if you wan't to force the code to be shared (like GPL) or a less restrictive MIT style license with your added copyright notice requirement. For webservices provided over a network there is the AGPL license. Since the normal GPL only requires source to be provided when there is binary code distributed, the AGPL requires it to be accessible by anyone interacting with the software).
It's worth looking at the following:
Here is the Open Source Initiative's "Open Source Definition".
And there's the GNU foundation have a Free Software Definition
Also you shouldn't be writing a legal license unless your are a lawyer, or at least consult with one. At the very least you should ask in the the OSI mailing lists.
EDIT: One more thing is it's probably better to have an advertising badge rather than a copyright notice. An advertising badge makes it obvious that you make the forum software and gives people somewhere to go if they are interested in the forum software itself. It shows your not somehow responsible for the website. As such can drive more people to your company. Also it's possible that the copyright makes a claim of owning all the copyright on the site itself rather than just the forum code, more extremely it might even be that making such a claim is somehow legally impossible and invalidates your entire license but I'm not a lawyer.
If you can, use one of OSI approved licenses. It's easier for you, and it is much easier for your users.
Look at truecrypt for example. It's a brilliant opensource software, but because it has it's own license it cannot be part of Ubuntu for example. In consequence, users cannot simply click and have it installed. They don't get automatic updates, etc. It's all only because the license...
So, once again - if you can, pick one of the OSI licenses and make the World better.
Point 5 of the license shares the following statement of JSON License.
See discussion with the problem of the license. Basic, it boils down to how one jusrisdiction defines what is illegal, thus making the license hard to enforce.