From blog:
If we have GPL Schema and someone modifies it without notifying us (which they are allowed to do) and makes a document following the altered grammar and tries to input it into the system. The software checks it's validity against the Schema it has and determines it is not compliant and the document is not processed, because the software doesn't know how to process it.
- That's not the problem. "The software" is not one thing as you suggest. There will be competition there too. There will be a modified schema, AND modified software, because a self-interested fork almost always involves both. The modified software works with and even EXPECTS the altered grammar, and now you have a fork, and if the promoter of the new fork (Microsoft, Monsanto, oilcos) is powerful enough, they get content poured into the altered grammar that we can't get first, and (depending on content license) can't even copy.