It's two things I thin:

1) They are anal about software downloads. They are afraid that if they have people linking to other sites downloading software they can get into legal trouble.

2) We are the "new kids" on the block. They don't like us. lol

Either way... the way I see it is I look at the purpose of a forum: members providing information on a variety of subjects. At what point do you put a limit on that information? Whether or not you link to other sites, people will leave if you don't have the info you are looking for. But if you provided the link in the first place to where they ultimately found their info, they are more likely to come back.