Paypal, Recurring Billing, and ActiveMerchant

First, does Paypal require a user to register for recurring billing with Website Payment Standard?

With Website Payment Standard, you direct your customers to fill out their information on paypal's site. to me, that's kind of cheesy, but your mileage may vary. If you are going to be making some money, it's well worth integrating it into your site and upgrading to Website payments Pro, imo.

I planned to use ActiveMerchant but I found some blogs that says ActiveMerchant doesn't support recurring billing from Paypal. is this true?

It doesn't out of the box, but you have to create a new Module class that gets added into Active Merchant, plus the views and really, it's a lot of work. No should say to you that it's easy to do, because they are either liars or really good at programming.

I found the SASS Rails Kit by railskits.com, which says it supports recurring billing with Paypal's Website Payments Standard. If I purchased this, would the code be clear enough to understand and implement in my own site, or is it kind of packaged deal for starter sites and not existing sites?

Sure, it may be clearer, but if i recall, they use a referential transaction to 'fake' recurring billing, as of this august, when i wrote my solution. As for existing sites, you may have to gerry rig it into your existing app, or create it around it. TBH, the $2XX price tag scared me off.

I found a lot of blog with help with recurring billing with ActiveMerchant, but using Paypal's Express Checkout. I read about Express Checkout on the Paypal site, but I still can't quite understand what it is, and how it's different from Website Payment Standard. Can anyone explain this in a simple way?

Paypal Express requires you to have your own merchant account. A merchant account is where your money will end up and is the only for your customer's bank account to speak to your bank account easily.

Website Payments Standard uses Paypal's own merchant Account through your Paypal Account, in order to pay you.

Again, imo, pay the 30 bucks and go with Website Payments Pro.

If we are discussing how to do subscriptions using a Ruby on Rails /ActiveMerchant environment I am not sure why no one has brought up Freemium, which is a sister project to ActiveMerchant that focuses on subscriptions.

We're also developing a subscription based site and this looks pretty interesting - http://chargify.com/. Could save quite a bit of coding time.

Express Checkout is the same as Website Payments Standard. It is the method of redirecting your customers to PayPal to collect their payment info. There's a simple implementation of just creating a form that posts directly to PayPal, and you can optionally use IPN to get info about the transaction. There's also an API for Payments Standard, that lets you set up the transaction with PayPal behind the scenes, then redirect your customer to PayPal, then query PayPal via the API for details on the just-completed transaction. The SaaS Rails Kit (I'm the author of it) uses this API.

Website Payments Pro is PayPal's offering that lets you collect the payment info at your site and pass that info via their API to PayPal. You then get information about the transaction via the API. The customer never leaves your site. PayPal's TOS require you to offer Express Checkout even if you offer Payments Pro. Payments Pro costs $30 / mo. (as I recall) and requires you to fill out an application for a Pro account.