I received more information concerning Kesäkoodi, the Finnish equivalent for Google's Summer of Code.
Now that they have gone through the submitted proposals, I have been qualified for the second round. That is, I should make a more through proposal for the project. With this proposal, I may get into the final round, where I should present this project plan in front of live audience... (no, I don't know why it has to be this complicated)
Anyhow, now they do want to have some mentor / contact person from Inkscape side. As I understand this, this contact person should provide COSS (organizers of Kesäkoodi) with some comments on my work. I don't know for sure though, they haven't been too verbose on that.
The project I am planning is to further develop the filtering system and to implement a couple new filters. I will post the project plan in further detail, as I get it done and translated in English.