Reinstall mac os x 10.10 yosemite; never had mac os license assigned to my icloud account

Recently I found an old MacBook, probably from 2009 at my company's storage place. My boss allowed me to take it and I really want to try it out. The thing is, when I try to reinstall mac os with Recovery boot (command + R) I have to login into my iCloud account. After I do it, it says that the service is currently unavailable. The thing to mention is that I never had any mac os assigned to my iCloud account. I've read some forums, but I want to be sure. Should I buy a license for some Mac OS on apple's site and then try to login again and then it would work? Thank you.