Christian,

1) is there a way that I can link from multiple websites (the prd pages) to the one registration form and pre-setting the membership level? So that the user does not have to figure out which one it is.

You can use the 'Special Registration URL' setting for this in the Membership Plans. Using this, you can set which Membership Plan will show on the special registration page. For example, you can have user/register/Silver, user/register/Gold, etc

2) when a user has payed via paypal but did not click on "return to seller's website" the user is not registered.

When I test this, the user is still created successfully, and sent their login info, and the role is added to the account. The only thing that doesn't work is the automatic login (which is expected since the user did not return to the site. But the user is able to enter their username and password that they were emailed and login to their account just fine. What settings do you have set in your admin/user/settings settings page? Attached is a screenshot of mine.

3) I have to synchronize a 2nd website when the user is assigned a special role. What is the name of the hook to be used?

You can use the following hook example function:

function yourmodule_ms_membership_signup($account, $membership, $m_plan) {

}

This function gets called whenever a new membership is created for a user. There are also hook_ms_membership_payment, ms_membership_ms_membership_cancel, and ms_membership_ms_membership_expiring which take the same arguments.

4) after registration the user is not directly registered (that is done only after a payment is received). But in case, the user stops on paypal I still would like to have the user in the DB for email marketing reasons. Any solution?

The user account is not created because many people don't want user accounts created for people who ditch the payment process (they don't want free user accounts and they don't want to have a bunch of dead user accounts). One thing you can do is let users sign up for free, then if they want to upgrade to a paid plan, they can do so from their User Account. I will give this some more thought though, and may consider adding a setting to create the user account or not immediately upon registration and before payment for people who want that...

Sincerely,

Leighton Whiting