" in this program women are encouraged to do so with an internship. There is no exclusion of male developers in any project, just an incentive to a certain group which is grossly underrepresented. "
Certainly there is an exclusion from the internship.
iow this is a job opportunity: 'doing some work and receiving compensation for it', and a class of people are excluded from applying based on their gender.
If the program was about encouraging women to _volunteer_ to open source project, or encouraging women to _apply_ to GSOC, for example, and helping them to be successful GSOC student... that would be a completely different story.