Knime Modelling - Open source Policy

Can i use Knime for create my models (as it is an open source software) and just export the result in a PMML format?

Submissions are only accepted and scored if they conform to the submission format, which is a CSV containing predictions. As for what software may be used, here is the relevant section of the official rules:

OPEN-SOURCE CODE. A Submission will be ineligible to win a prize if it was developed using code containing or depending on software licensed under an open source license: