If what you are trying to do is displaying any webpage on your own browser using the Safari component you already have the rights to display it. If the owner of the content doesn't want you to display it the webpage would require a username/password to access the content. This is an implicit "contract" when you create a public site on the internet, anyone can see it/use the information provided. If there is an explicit ban of some domains due to government laws your application will not be able to access the site from that location (like use to happen on some mid-east countries/china) but the block will be on the physical network and you don't need to worry about it.
If you can access the domain from the application in any given location, you can display the content "as is" without any modification or claim of property, this is probably not obvious but you cannot claim that you produced the content, you can however display it and use it. IF the site has a protection requiring the user to provide a username/password, you can still display the login/home webpage without any explicit permission, this permission is already granted because it is public. Once the user of your application inputs a username/password "his" session will be granted the required permission to access the remaining content, again since the server sends you the information you can still display it "as is". In the case that your application stores the username/password for later access you need to explicitly inform the user about this, moreover he needs to agree on that. You can use those credentials to access the site later for that user. You cannot store the username/password to automatically login a user different than the owner of the account nor use yourself the contents of the protected webpage trough any means (i.e. scraping and storing for later use).
In short, if you can access the website you can display it as is and that's legal. If the site is protected you can still display what the server sends you (probably home page + some login webpage/option). You can let the user interact with the webpage like any other browser does and he can log in to the protected webpages and you have the right to display that content for that user, not to store it or duplicate/publish/etc.
You can not: show a webpage and claim you built it, unless you have explicit permission from the owner/legal representative of the webpage to do so. You can't even change the webpage to "disguise" it is as something that looks like you built it, without you claiming you did.
For a regular browser-like interaction with internet in general, you already have the rights to display the contents of the webpages that are publicly accessible.
Hope it helps!
