Braintree is described as 'payments platform that lets you accept payments with credit and debit cards, PayPal, Apple Pay, Android Pay, Venmo, Bitcoin, and whatever's next' and is an website in the Business & Commerce category. There are more than 50 alternatives to Braintree, not only websites but also apps for a variety of platforms, including iPhone, Android, Windows and Mac. The best alternative is PayPal. It's not free, so if you're looking for a free alternative, you could try Amazon Pay or Ripple. Other great sites and apps similar to Braintree are Flattr (Paid), Stripe (Paid), Payoneer (Paid) and DASH (Free, Open Source).
Flattr is a social micropayment service, that makes it easy for you to "flatter" things on the internet that you like. When you're registered to Flattr, you pay a small monthly fee of your own choosing.
Stripe helps you create any type of payments flow—from e-commerce to recurring billing and everything in between. Stripe enables you to accept payments in minutes. Stripe makes recurring and subscription-based billing easy.
DASH is an open source peer-to-peer cryptocurrency that uses a system called Darksend to add privacy to transactions. It allows you keep your finances private as you make transactions, similar to cash.
GNU Taler is a privacy-preserving payment system. Customers can stay anonymous, but merchants can not hide their income through payments with GNU Taler. This helps to avoid tax evasion and money laundering.
Cardano is a decentralised public blockchain and cryptocurrency project and is fully open source. Cardano is developing a smart contract platform which seeks to deliver more advanced features than any protocol previously developed.