Offerpal and Yahoo are announcing today that the third-party monetization provider will be available for developers on the Yahoo’s application platform. It’s a deal that makes sense for both, but the question is still this: will developers succeed in finding valuable new users through Yahoo? Developers will need Yahoo to help deliver large audiences to monetize through the advertising offers or payments options that Offerpal provides.

Yahoo is challenged by the growth of Facebook and other online communication services like Twitter, that displace its position as the central web portal in people’s lives. Like other web companies, Yahoo is trying to attract social game developers to build on its developer platform, the hope being that games will bring more people back to its site more often, just like apps have for many users on Facebook.

Meanwhile, Offerpal is, like most other virtual currency monetization companies on Facebook, not yet included in Facebook’s expanding in-house virtual currency, Credits. Facebook has been its core market, but the company increasingly looks like it is going to make Credits the exclusive payment option for virtual goods in applications on its platform. If that happens, Offerpal will be forced to do business elsewhere.

Like other offer companies, it has already planned for this possibility by working with online gaming companies and other social platforms. Yahoo’s platform, with a string of integration points for social interaction and large user base, is especially interesting. The problem is that it, as with every other platform except for MySpace, has not yet been able to prove itself.

It does already have social game developer Zynga on board, through a recently-announced deal. Presumably, Offerpal and Zynga — two long-time partners — will be working together here.

Yahoo, like Google, AOL and other older web portals of sorts, is trying to remodel its existing set of sites and applications to have more social features. As opposed to Facebook, MySpace and other social networks, they lack a central social identity for users to orient themselves around, even though they have been working on improving this for a while. As Yahoo tries to make its core service more social, it is also giving third parties more access to what it has going.

It is providing developers with access to users’ contacts, the “social directory” (a variety of personal information), user status updates and other activity; the platform also comes with support for OpenSocial-compliant apps. Developers can currently communicate with users via the Yahoo home page, My Yahoo, and the Yahoo toolbar.

Whether or not Yahoo becomes a serious social gaming platform, the platform idea make sense — and considering the friction some developers and third parties are feeling with Facebook, the timing could help, too.