The sad thing is that it is a bad business decision to not submit changes back to an open source project. If your company makes a change, the best outcome for the original project to adopt the code and assume the cost of maintaining the code. The worst (most costly) is your your company maintaining a fork. Never mind the loss of recruiting opportunities.
Agree completely: which is why I wouldn't worry about 'proprietary forks'. For almost any reasonably popular language, the community version's progress will quickly outstrip almost any company's version. If the company's smart, they'll try and stay as close as possible to the original, submitting patches and so on.
