We have created custom PayPal implementations in the past, but we don't really do it anymore. Basically a programmer has to create a web-based form that has the options, and then pass that data to the PayPal checkout form.
Take a look at our Frequently Asked Questions page. It's a great place to start if you have questions. In the meantime, here are some common questions we get from customers.
There is a lot to consider when choosing your donation payment processor. You will want to determine which features are "must-haves" and which are "nice-to-haves" when making this decision. Each payment processor has its pros and cons, and in the end you'll have to decide which one best meets your fundraising needs.
This page that we send your donors to, which is often a mobile-formatted PayPal checkout page, is called a "donation link." "Link" is just another word for "URL" or "web address." So, when we ask for a donation link, we're asking for the web address, web page, or URL where the donor can actually enter her credit or debit card info and send you funds.