Teespring is owned by its original founders Walker Williams and Evan Stites-Clayton.
According to their site, Spring for creators is free to use. You set your selling price and keep 100% of the profit. Spring's fee is included in the base cost of the product. For example, if the 'base cost' of a t-shirt is $10 and you set the selling price as $24, you would keep $14 in profit.
Teespring is a free online platform that lets you create and sell over 50 kinds of products with no upfront cost or risk. Teespring handles everything, from printing to shipping to customer service. You set your own selling price for the items you've created and decided to sell. You keep 100% of the profit. Teespring makes its money by taking out their fee, which is included in the base cost of the product. For example, if the 'base cost' of a t-shirt is $10 and you set the selling price as $24, you would keep $14 in profit.
Yes, Teespring is a legitimate business, not a scam. It has raised over $60M from top Silicon Valley venture firms such as Andreessen Horowitz and Khosla Ventures. It was also awarded the #1 Product of the Day on Product Hunt on December 23, 2013. The company started by making it easy to design and sell custom t-shirts. Their "secret sauce" was handling all of the heavy-lifting in terms of inventory, marketing, and logistics, so that anyone could sell custom tees. They have since expanded their social commerce offering to allow their customers to design, market, and sell custom merchandise of all kinds.