Do Astro developers sign any kind of exclusivity or non-compete contract that would make it harder for them to leave to work for another company?

A former company I worked for hired some excellent Central American developers through a company, and I later learned those guys had all signed contracts that made them give more than half their salary to the outsourcing company for two years, and if they wanted to leave before the end of two years, they had to pay a lump sum that was about a year's salary.