I think that there is a general goal of attracting more developers to Maemo which is quite separate from the specific goal of attracting iPhone developers. I suspect it is more beneficial to work on this general goal (at least in the long run).

Not to over-generalize, but for a mobile platform to be attractive to developers, some combination of two factors is necessary:

1.) Easy to develop for
2.) Rewarding to develop for

I realize that sounds obvious, but the two are inversely related. A developer may be more willing to write an application for a platform that isn't all that rewarding if it's easy to do, and conversely, they will rationalize difficult development in an environment where the reward potential is great.

iPhone development seems to understand both. Developing for the iPhone is fairly easy (I am referring to the actual development, not the process of getting an application approved), and considering the install base of the platform, as well as the public and media attention surrounding it, it is quite rewarding.

Maemo is sort of the worst of both worlds currently. I'd argue that it's not all that easy to develop for (easy being relative, it is in fact not incredibly difficult to develop applications for Maemo), and other than the philosophical satisfaction one might get from sharing their work, not all that rewarding.

Dealing with the second part (rewarding) is entirely dependent on Maemo devices becoming more popular. With the release of the Freemantle device (whenever that is), it appears Nokia is targeting a larger market. This bodes well for developers. While Nokia has said that they are very pleased with the adoption of the current tablets, I would be very surprised if their adoption has been large enough to make them attractive to third-party developers.

Speaking to your specific question about encouraging iPhone developers, I see that as a tough proposition. The bottom line is that the vast majority of iPhone developers are opportunists (I don't use that term derisively), they have no underlying loyalty to the iPhone, they just see it as the best way to get their applications out there (or the way that involves the least amount of work for the most reward). If the story about Microsoft paying developers to port those apps to the Zune is true (which would be a good move on Microsoft's part) than that merely changes the second part of the value proposition (it increases the reward of writing an app for the Zune to be sufficiently greater than the challenge of writing it).

In iPhone App world (a neighboring but not necessarily friendly ally to Free Software Maemo world) developers are primarily swayed by the thought that they can make a bunch of money by selling pretty straightforward apps. While certain examples have borne this theory to be true, a lot of developers find that the "race to the bottom" in regards to pricing dis-incentivizes working on complex or large applications.

I don't see how to make these people want to develop for Maemo (short of Nokia offering them a bunch of money, which I don't see happening). As it stands, there is no commercial market set up (and I suspect if one existed, it would be very unpopular with a lot of the community here), no way to prevent piracy, and no large user base.

I also don't necessarily think that's a bad thing. While people who dismiss the iPhone app store as "a collection of fart apps" are being incredibly obtuse, the reality is that it is predominantly a marketplace with applications that have a fairly simple functionality (albeit implemented in a useful way) or application which allow a mobile experience of something that a company already has established (slingplayer, skype, qik, etc.)

I should also say that I personally use an Android phone (not for philosophical or technical reasons, merely a matter of cell provider strengths where I live) and I find their development process to be about in the middle. Applications aren't as easy to develop as iPhone applications (mostly due to the sdk being in more of a state of flux than the iPhone sdk), but I would say easier than Maemo applications; and they aren't as rewarding as iPhone applications (as Android phones, while increasing greatly in number, still aren't as popular as the iPhone) but have a larger potential than current Maemo devices.