The only problem you could solve is recruiting new contributors who want to port open source projects, as pressuring the current developers is highly counterproductive, doing the porting without help doesn't need any social networking, and collaboration on the software development itself is going to use different, established tools (most likely those of the existing project: forums, mailing lists, public source repositories).
This niche of making people port open source projects to different platforms is better served by more general software developer recruitment approaches (why focus on porting?): for paid work (I want a port of this library but I don't want to do it myself) there are existing employees who might be just assigned to do it, general-purpose job/contracting boards and targeted announcements and advertisement to experts of the involved platforms.
For the delusionally small niche of volunteer work (If you don't know what to do, maybe you'll decide to port these great libraries to neglected platforms) interested parties are perfectly able to research what would constitute a good porting campaign for them in terms of effort, utility, learning opportunity, etc.