Polar

Polar is open-source billing infrastructure for software, acting as merchant of record: it handles global VAT, GST and sales tax rather than leaving the liability with you. It covers subscriptions, one-off purchases, usage-based billing and licence keys, and can gate access to a GitHub repository or Discord server as the thing sold. Framework adapters and Apache-2.0 SDKs for Node and Python ship with it.

We track it rather than run it. We list it as the option for developer-facing products sold globally by a small team, where tax compliance across dozens of jurisdictions would eat more time than the product does. The repo and Discord gating is the part we watch, because it matches how small software gets sold now.

Paddle and Lemon Squeezy are the established merchant-of-record alternatives; pick either for a longer operating history behind the tax handling. Stripe is the comparison for everything else — more capable, but you stay the merchant, so tax is calculated for you and still owed by you. Chargebee answers the case where subscription management and dunning are the real problem. Polar is right when you are small, global and want tax liability off your books. It is wrong for enterprise invoicing and bespoke contract terms; read the payout and fee terms before you commit.