The Grateful Dead sure suffered from this.
The Grateful Dead supported it.
What it comes down to is respect for the band's desires and their rights, because as the creators of the performance in question they superceed the individual's desires and rights. If the ban is cool with it, fine. If they are not, that's fine too, it's up to them. But we gotta either follow their desires or go somehere else for our entertainment.
What if you wanted to get a recording of a show in your home town, but the official tour DVD was from the LA show?
So what? I'd like to nail Jessica Alba too, but it ain't gonna happen (I guess someone's beat me to it now anyway

) and I accept that and move on. You can't always get what you want. That's life. Deal with it.
And just because they are not putting out a DVD now doesn't mean that they may not have plans for another project down the road that they're saving up material (and public demand) for. You have no idea what their game plan may be, and to assume that their concert in your town is open game is incorrect. That remains *their* property to do with - or NOT do with - as they please. And to just take it from them is no different that assuming that if Ms. Alba is not currently seeing someone that it's Ok to just go ahead and rape her against her will. Because that's what YOU want.
Just because the Dead and Phish and the like put it out to anyone who wants it like Philippine crack whores when the fleet comes in does not set a precedent for the whole industry.
As to the OP, what's to master? You cot a crappy audience recording of a live concert. There's not a whole lot you can do other than EQ the begeezus out of it as required. Don't be afraid to extensively cut, but keep the cuts narrow; no big lobotomys. Some multi-band compression - or better yet, multi-band expansion - may help a bit, but frankly, you're going to be mostly stuck polishing a turd.
G.