Looking at the above picture, you will notice that he always promises "Access to ..." the game at each level. He never promises that the pledges will have a new game each month, but they will have access to said update. If there is no update, then there is no "Access" to be given. The only things pledges will definitely be given are:
$1:
A big "thank you." No really.
$5:
Vote on monthly high resolution pinup renders (here I will give you, he should be making monthly votes).
$10:
Early access ... (Need i say more?)
$20:
Complete walkthrough and cheat codes.
$40:
Alpha tester status, access to the test-render Discord channel...
So, as you see, the only thing he promised and is technically negligent on is a vote on these monthly pinup renders (which he never promises to provide). So, legally, all he has to do is make a monthly vote.
All that aside ... have you ever had anyone try to persuade you to do something for them, citing a lawsuit if you do otherwise? And if you have, how willing were you to give your best when you performed said action? And how likely would you be to engage in future activity with that person?
If you really, truly, want Irredeemable back again making this Visual Novel, perhaps a different sort of approach might actually convince him to do it. Maybe if instead of flaming him and crying about it (which could make anyone say "fuck them, I'm done"), we could simply ask him to come back. If we can't do that, perhaps just closing our foaming, babbling, drooling mouths will do the trick.