GSOC slots are given out to an organisation. That organisation is the Plone Foundation.
The number of slots is based upon:
- the number of viable project proposals that students come up with
- the mentoring capacity of the organisation
in the end, the organisation applies for a number of places, and then Google decides, taking the above into account. Some organisations have 20+ places, others one. Reputation and track record in previous editions play a role here as well.
It's essentially a very human-based process, with the GSOC organising team being very approachable and hands-on, although also strictly following the rules (as they must and should). So if Pyramid had places before on a regular basis, and in future (not this year) would apply 'under' the PF umbrella, that would surely be taken into account by the evaluators. So I see no issues there in future, and certainly it woudn't 'limit' the places in any way.
Bottom line: it all comes down to having enthusiastic mentors, viable and well-defined projects and students with a believable proposal. You give some, you get some. That's the idea behind GSOC.