use forum login in other parts of site?

You do need a seperate account to comment on Phandroid.com. However, you don't need to make use of any of the cross site authentication options such as Google/Facebook/Twitter and so on. If you make a normal disqus account, you can avoid all of that. (Disqus is the commenting system we use, not some obscure social network you haven't heard of ).

If you sign up for a bog-standard Disqus account, you'll still need to provide an email address, but it is not actually tied to your google account. I.e it's no different to using your gmail account to register on the forum. (Although it is worth mentioning that your disqus account can be used on any other site that uses the same commenting software - you may or may not want to use the same account elsewhere).

We did actually suggest to the admins that a shared login for both sites was a good idea. So whilst I do agree it's a good idea, unfortunately I don't think it's going to happen.