I think it's time we think about selling merchandise. I've looked into T-shirts, here are thoughts about how to do it.
I'm looking at the upper-market. It's more efficient to sell fewer, expensive T-shirts, with a clear indication that it's mostly a donation. It's less work (time...) but most interestingly it makes us stand out from the rest (, ,  etc).
So roughly looking at a good-quality stuff priced at EUR 18 - 20 . The US dollar markets are almost out of range because of the current disadvantaging exchange rate.
I'd go for non-geek stuff. No joke, no risquÃ© tagline, no reference to "root", not white text on black. Rather, something one could wear half-casually.
3. How to do it:
We have 2 possibilities so far.
a) Do it ourselves. Which is: do it myself. I had an estimate for a quick design, for a minimum order of 50 I can get them at 11eur each (everything included). Add 2eur shipping in the EU and 4eur to the US, if we sell them at 20 eur we can break-even at 27 t-shirts. If we sell 90% of them this will provide us with 225 eur out of it. Enough to pay 2/3 of our hosting expenses.
b) Do it with cafepress.com. It's much easier. My fears are that standing out will be much harder, because the "donator-customer" is driven away from us into a separate store. Also the probability that the customer is driven away on other "cafepress linux products" is higher.
In any case it's unbelievably hard getting money inside GLM's bank account. Welcome to France. The "association" status set of regulations makes for a great disincentive to "competing" with real companies. Paying myself and Gustavo legally is yet another story - that'll be for another thread. I'm battling with paperwork, authorizations and administrations.
All of this to say, it's extremely probable that we'll have to give a T-shirt as a gift for a donation. This will at least enable exporting T-shirts to the US without paying extra tax. CafePress might be a good way to sell T-shirts in the US, while the self-made solution might be good for the anywhere else.
5. One proposal
I had a go at a design and here is what it looks like (front then back)
(links to source files for your pleasure. Please don't redistribute).
The GNU is GPL-licensed, so a paper mention of the license and url to source file would be included with each T-shirt.
I trust the manufacturer I contacted highly. They provide two stores I know, each of great respectability. They can print up to 6 colors (no gradient) and need 2-3 weeks for delivery.