Spree Commerce announced today a new round of funding in the amount of $5 million.

This is the company’s first institutional round. The Series A was led by Thrive Capital with participation from Zappos founder Tony Hsieh’s Vegas Tech Fund, Red Swan Ventures, and existing investors True Ventures and AOL Ventures.

Spree Commerce makes open source software that helps online retailers quickly build out full-featured, customized storefronts on the web.

As a top project on GitHub, Spree is one of the most-used open source technologies in the world — and certainly one of the most popular open-source tools for online retailers.

“Almost 500 developers have contributed to the platform, with new features contributed by almost 200 of those developers in the past 12 months alone,” according to a statement from Spree, which also said, “More than 45,000 retailers in over 100 countries have chosen Spree Commerce to power their online business, including established and emerging leaders such as Bonobos, 3.1 Phillip Lim, and Blue Bottle Coffee.”