The heart says yes
The heart says that they should. There is already a Notes client for the Apple Mac family. I don't know what proportion of Notes clients run on Macs, but it must be worth Lotus's while to do it, otherwise they'd have dropped it when they dropped all the other clients. I can't be sure, but I would have thought that the market future for Linux is at least as good if not better than that for the Mac. So once they have a Linux client, it should be self-supporting, in the same way that we can assume that the Mac client is.

There's also the fact that, in my opinion, browsers don't do the business for the kind of interactive workflow and collaborative applications anywhere near as well as the Notes client does. Just consider the development time, the rich text editing--crucial to collaborative applications--the extra hit on the server, security issues, and the offline abilities of the Notes client. Compare those to browser solutions. Things like the DHTML editor in Internet Explorer, SSL (Secure Sockets Layer), and DOLS (Domino Off-Line Services) just aren't as simple and coherent as the Notes client, which means that they cost more to develop and support. And maybe we just don't build the applications, which constrains the ability of our businesses to move forward. iNotes does mail, but it doesn't do all the other applications that Unipart has, and that is the biggest barrier to Unipart using Linux on the desktop.

So, for those people who want to use Linux, the lack of a Notes client means that they lose out on the things that Notes does better than anyone else. They lose out because they don't get the benefits to their business, and Lotus loses out on licenses. I don't see all those lost Notes licenses being replaced by HTTP-based CALs, either. They're just lost. To my mind, a Linux client would, with the right marketing, bring new client licenses to Lotus and not just replace existing licenses with a different implementation. It certainly would mean that they wouldn't get lost to Microsoft!

The head says no
However, the head says that maybe they shouldn't. The whole Linux question has been asked in the context of freedom of choice, specifically freedom not to pay Microsoft license fees, and freedom from the worry of what new costs might come in Microsoft's next licensing version. This search for freedom has taken people to alternative office suites for Linux--of which Sun's StarOffice (at http://wwws.sun.com/software/star/staroffice/6.0/) gets a lot of mentions. Star Office is not free, but it's cheaper than Office, and it runs on Linux. As an aside, Lotus's SmartSuite still exists, does everything that Office does (including read and write Office files), is a lot cheaper than Office, and runs on Windows, so savings on Microsoft licensing can still be done without the expense of moving away from Windows.