So far we've been able to keep our costs fairly modest, but as the case (now cases) go to trial the costs will likely balloon rapidly.
It's always a concern though because support might stop at some point, especially since the total cost is more or less unbounded. For example, in the defamation lawsuit against Peter McCormack his sponsored pulled out after the funds expended crossed a million UKP sticking Peter in the middle of some complex and expensive litigation and forced to withdraw most of his defenses because he couldn't afford the cost of them.
Fortunately, at the 11th hour he was able to prove that the claimed damages the case rested on were totally fabricated (the plaintiff claimed to have been dis-invited from academic conferences; McCormack got a statement for the organizers that Wright's submissions were rejected by peer review for being rubbish), resulting in McCormack ending up with a 1 UKP judgement against him ... plus some 900k UKP in legal costs (which he's currently fighting to get dismissed).
A challenge future fundraising may face is that the time-scales of court are not compatible with the attention span of the public-- the number one thing I hear when I have updates is "oh, is that still going on?". The second most common is "that guys a joke-- just ignore him, he only wants attention". Well, I wouldn't argue that he's not a joke, but even a joke can cause tremendous damage especially when everyone's reaction is to ignore it.
The opensats fundraiser was able to raise about $1.5 million dollars for hodlnaut's defense, which on one hand is a tremendous success--- but on the other hand is about an order of magnitude too low. Which is why I'm attributing problems here to the legal system and inadequate protections of open source licenses in light of them (MIT's waver of liability is arguably stronger than most too) rather than saying the community hasn't stepped up in support.
I presume you are referring to https://wikipedia.org/wiki/Pound_sterling ? If you are doing it because of political beliefs, perhaps avoid that on HN, and should maybe using the £ symbol would be a suitable compromise instead? Although maybe it was just a typo, given you used “dollars” later to refer to USD
(And I'd never heard of anyone calling it UKP as a political statement, but presumably it would have something to do with Northern Ireland being a part of UK but not part of Great Britain.)
What a shame it would be to lose a transparently baseless case through mismanagement. Ironically, it's the strong cases that you're almost sure to lose that you might as well phone in or not defend at all.
In this case the plaintiff does everything he can to jack up the costs, including bombing the case with irrelevant stuff, gaslighting, etc. The courts have caught him doing this in other cases and chasized him in their rulings (complaining for forgeries and perjury) but the recourse so far has been confined to wrist-slap grade consequences.
A lot of the structure we have in our courts (both in the US and UK) to ensure good faith behavior is setting things up so that cheating makes you ultimately lose the case. But if you didn't seriously expect to win on the merits (instead only by the other side screwing up) and were mostly just trying to use the process to cause harm then it doesn't really matter if your forgeries and perjury ultimately cause you to lose.
So for example, in Wright v McCormack, McCormack was able to show at trial that Wright's claims of damages were intentionally falsified. This got McCormack a 'loss' where he only had to pay 1 pound and where he was awarded his fees for the trial (well probably 70%, that hasn't been decided yet)-- but in the interest of finality the trial court declined to reverse the 900k pounds in fees he had to pay for the other sides costs in earlier motions.
This also potentially provides an additional avenue to hit your opponents during a SLAPP-- sandbag your costs so that whatever the opposition does have to pay on motions they lose are ruinous, and also so they have to spend a lot defending themselves so that 30% they can't recover is also ruinous.
Full cost on trial like this-- with discovery and experts, etc-- may be on the order of 10 to 20 million pounds. Would you expect a volunteer open source developer to be able to pay a non-negligible part of that, on top of the substantial imposition on their life and time that fighting the case and winning entails?