We enhance open source software for use on our platform. We'd love to get our changes into upstream, but it isn't always easy to make the time for that. As you

We enhance open source software for use on our platform. We'd love to get our changes into upstream, but it isn't always easy to make the time for that. As you say, all kinds of issues are raised by having our own variant, but fundamentally, if we need to fix (or add) something, we need to do it. Merging from upstream is just merging. It's a pain and a cost, but we can choose when to do it (largely) and if it's too painful then we can spend the time to merge up.