I think this is one of the few projects where I strongly, strongly say no: don't put this on Ovi. If it was a program that is not even that necessary, like Columbus, which is just neat to have, but doesn't change the overall quality of your device use in every activity, that's one thing.

But this is something that significantly increases the quality of N900's day-to-day use. In every program with text input. It's been one of the most-wanted, most glaringly lacking features in the entire N900.

Here's the pragmatic statement: If you release this closed source and on Ovi, someone here will eventually act on principle and make another vkb that does what yours does. If you release this open source and on Ovi, it's less likely, but possible, that your project will get forked. I personally hate going to Ovi from the N900, then waiting 10 minutes after pressing download, until it eventually launches the horribly slow Hildon Application Manager, etc; so if you market it from your own site, especially include it with source code, that'd probably be best - yes it'll get leaked, but admittedly forcing people to give a small payment does make more people who'd normally be on the fence okay with 'donating'/paying.

If you release this and make this open source, yes, you're not going to make as much money - you have my word that when I have a job you'll be on my donate-to list, but indeed the unfortunate thing is free stuff gets less money because people are selfish.

At the end of the day though, the great thing about the open source process is you don't have to do it alone. It's not equivalent to the paid programming process because as soon as your code IS open, people can contribute. Seriously, this would've probably already been ready for release a week ago if you had put it on GIT like MohammadAG suggested, because other members of the community would have leapt on it. Columbus and Sleep Analyzer, for instance, get screwed because they're not general enough to matter to everyone, so their developers get less-to-none outside contributions. But this is something just about everyone who owns an N900 could probably say they'd like to have.

At any rate, my opinion is you're better off in the long term making it open source, and at least eventually making it free. Your flow of money will stop when everyone who has an N900 has stuck this keyboard onto their device. And then that's it. Unless you charge for updates. (Also, from an economic stand point, I think you'd benefit from making it one euro. Apple App Store apps that cost 99 cents sell like beers at a pub, and ultimately get more buyers because they're cheaper.)

I think if you open-source it and allow for contributions to be given freely, you'll find that pretty quickly, the keyboard will receive development contributions from others, and in general, can outgrow your best expectations/hopes for it, not monetarily but in quality/versatility, etc.

I know living in a capitalist world has the ugly requirement of getting money. Open source development is one of the few things that challenges that: One's contributions are information and life-quality increasing software, but one reaps the benefits in that plenty of other projects others have open sourced are free as well: seeing how other code works, using that code or that software to make your own life easier, etc.

What I really want to say is, before making your final decision, instead of just considering how much money you could or won't make depending on how you release this, also think of how much money you have saved, because open source programs were available. Overclocking, IPv6 support, ridiculously broad filesystem support, Host Mode, FreOffice, Columbus, the 3-4 or so voice navigation solutions instead of Ovi Maps, all of which are open source? fMMS, Sleep Analyser, Conky, HealthCheck, FApMan... I don't even know what to list off anymore because of how much useful to someone somewhere software is available on the N900, entirely for free, but I'm sure you've benefitted from a lot of those.