You can donate when sending a payment in the client
But would you donate under the present circumstances bitpop? Possibly you would, but knowing what I know about the intended changes to Armory (which is old information now, alot may have changed since then), I can't justify it for myself. And I can see how others might feel like that without knowing any extra details; it's investing in something with too much uncertainty in the return. You may end up being confronted with the retail price of the closed-source version the following day.
No I'd see if I'd want to donate to a forked project or a retail version or whatever happens. I'd gladly pay .5 btc for a lifetime license if it means better support and a better future. Then someone can keep patching the current open source one for donations.
Maybe just critical patches like the working with .11.1. It's already full of features. Goatpig gets to make a few Bitcoins and ethiopa gets to build his company with a steadier stream of income. I don't think it's a big deal. People can download the best and latest armory right now for free, but they can't expect it for life.