I spent much of my career learning proprietary software, only to have that company go from market leader to non-entity. Meanwhile someone gave me career advice about 20 years ago, telling me Unix was the future. Right about the OS philosophy, wrong about the branding and business model. Today I'm a big !FreeSoftware advocate. !FS hasn't had as big and fast growth as some proprietary SW companies, but !FS hasn't had the incredible crashes either. So, my advice is to learn something cool in the !FS world, get really good at it, and be prepared to keep learning new cool stuff all through your career.