What we are saying is that it is our policy that the work for hire doctrine (see http://en.wikipedia.org/wiki/Work_for_hire) does not apply to OSS contributions at Rackspace, and that we encourage all employees to become involved with a community.

If you work at a company bigger than 10-15 employees, check your employment agreement. Rackspace's stance on this is highly unusual (I think even unique) for a company its size.