I'm a freelancer and if i work for free, i do not have any money. So for me to be able to develop and share this freely, i would probably need some big corporation that is willing to pay me for working on it.
I'd also be interested in how those projects come up with the money to pay a professional designer. Roundcube looks very sleek, as if it was designed professionally.
BTW, what i'm developing isn't exactly a webmail client. It is an server-side IMAP gateway and a client so that you can use it completely offline.
I've contributed to this project and various others and I frequently had people either hire me to add features to a certain project I worked on/released or bought me a book or so off my Amazon wishlist.
Though one time a company actually paid me to work on open source, this is nothing that pays my rent (currently) and also not my motivation to work on open source in the first place. My main driver is that I use open source and I decided to give back. It also helps my resume though I never really needed that either.
As for RoundCube's design — thank you. I am not a 100% sure right now if "money" went towards the design, but feel free to drop us a line at hello~at~roundcube~dot~net.
> I obviously can't afford to give my work away for free, but for you to get maximum benefit out of it, it needs to be open source.
Meet others who can afford to give away their work for free:
http://squirrelmail.org/ http://roundcube.net/ http://www.xuheki.com/ http://www.horde.org/apps/imp
And there is more — google: webmail client open source