For a concrete case of this happening, see OpenSolaris after Oracle bought Sun. Since Oracle then owned all the copyrights for Solaris (since Sun had a contribu

For a concrete case of this happening, see OpenSolaris after Oracle bought Sun. Since Oracle then owned all the copyrights for Solaris (since Sun had a contributor license agreement that assigned copy right to Sun), Oracle was able to stop sharing source code updates to Solaris with impunity. This is all off the the top of my head so it might not be accurate.