On the FAQ page, Valve writes that there isn't a catch for the company not charging licensing fees. And while that's technically true, you do need to attend a $3,000 in-person training session in Seattle as part of the process. Valve hopes to allay that in the future, but for now, classes start in September, with Gabe Newell and Co. recommending that groups of industrial designers, and mechanical-and-electrical engineers attend rather than individuals. Those sessions start in September.
Honestly, they sound a bit like a college class and will have lecture and lab sessions covering SteamVR integration, troubleshooting and designing your own trackable objects. Are you ready to go back to school? Then maybe use Intel's recent advancement in VR tracking for inspiration.
Update: A previous version of this story said that Valve was open-sourcing the tracker. That is inaccurate, and the article has since been edited for clarity.