I read their Privacy Policy. They are quite explicit about what they plan to do to you. I raised the issue with them in an email (among 5 other issues). Their reply is in the header. Another issue I raised is that they expect me to accept undisclosed terms and conditions.
That said. I have worked with computer security at an advanced level, including consulting, training, penetration testing, design/implementation of x-platform server agents for monitoring and alerting, design/implementation of firewall. Once I designed an implemented a system to deal with NATO secrets (not very sensitive secrets, but still secrets) for a military subcontractor in EU. My computer is relatively secure. I follow best practices - and more. A hostile agent would decrease the security on my network. That was my first thought when I got that awful email.
Also, I don't get it why that need such a thing on my PC. I don't have credentials to production systems or production data. I am a software developer. I work with code and documentation. That's it. Anything I produce is reviewed by other developers and then tested independently by QA.
I am careful to be a freelancer, and not an employee, for several reasons. It means that legally I'm my own boss. That feels good (I have a great boss!) It also make it unproblematic to work on open source projects, without getting into discussions about who owns the intellectual rights to that work.