Its probably worth spending a bit of time on the whole issue of licensing "free" and "open" platforms before thinking someone stole something. Firstly there is the copyright in the original works, then there is how its sold or distributed. Software released as open source is not exclusively open source, the copyright holder can take his original works and license them as he pleases. He's also free to do similar works on any commercial terms. Open source means just that - the source code distributed rather than just the compiled binaries or object code. You cannot necessarily take open source software and build on it and you are not necessarily restricted from doing so either. It is entirely down to the terms of the original copyright holder. Next we have the whole issue of embedded works - here I build my work taking ideas from your work, which may have been taken from someone else's work. You may or may not have the right to embed other people's work in your work. Then you have the issue of whether the person who is the original author of the work, even owns the copyright to start. The vast majority of people contributing to open source projects, don't own the copyright of the contribution. Typically they will be employees in the industry or may even have developed the code for clients and feel its useful to share to the community. A lot of the big IT companies who build their platforms on the open source platforms, also contribute to the development of the open platform, as its in their interest to make the platform they are using as good as possible. Then comes the issue of fair use.. A huge spanner in the works for anyone trying to protect open works replicated in proprietary code.
So can a company take software distributed under open source / GNU and build it in to their proprietary platform and sell it? on the face of it no. In reality probably.
In a former role, I did quite a bit in the M&A part of a big software company and we spent a sh*t load of time reading every employment contract and scanning source code for embedded works.
If you look at computer history - almost all the big ideas were nicked from others.
My suggestions are not legal advice