It is, but it's a simple question of manners, permission doesn't HAVE to be obtained, but I'd personally much rather reach an amicable solution to this than have bad blood between the people involved. The fact of the matter is that Hard Light owes a great deal to the work that IPAndrews and the rest of the team put into TBP, and, although I don't always agree with him, I do understand how he feels, God knows, if I spent as long as him on a project, I'd be pretty sick of editing it too, and it's all too easy to assume that, since I am prepared to re-open the project once, that I was prepared to continue updating it. IPA is right in saying that you have to find a place to draw a line.
If an agreement can be reached, where the fans themselves can do these updates, and it can be endorsed by the team, not as an official update, but an official fan update, then it solves a lot of problems, no bad blood, the patch can be available in the TBP Forums themselves, which makes life easier with regards to obtaining it, and the fans themselves become responsible for maintaining the project they love, which is, after all, what the TBP team have been encouraging them to do for ages, by allowing them to create new campaigns etc, this is merely an extension of that.