I designed two of those challenges. We're successfully using it for international hires for quite some time now. We hand those out after you made it through tw

I designed two of those challenges. We're successfully using it for international hires for quite some time now. We hand those out after you made it through two telephone interviews, which should assure mutual interest in actually making hiring happen. We base our hiring decision on the outcome of the challenge. If you do good, we relocate you and your family, care for everything you need. Our success rate is around 30%. So I wouldn't say we ask you to work for free. We designed the challenge to be without example on github by giving extreme amounts of individual freedom in the task. Also, you're allowed to share the solution - but without mentioning the company name, so that other candidates cannot just google and find your stuff. Not everyone has a "significant" github profile. Actually the minority of people has such a thing. So many reasons for not having one. Current employer's policy, having a family, having non-IT hobbies, etc pp. Also just having such a profile doesn't necessary proof that you can solve the company's problems, because just looking at solutions of arbitrary problems doesn't give you any information about the constraints of the problem, how you solved them and it also doesn't put your solution to this problem next to solution of the guy sitting one desk away that solved the same problem in the same amount of time under the same conditions. (removed a stupid passive aggressive statement here, sorry folks)