It's more like an Affiliate Program or Partnership Program. But most people call it sponsor. Isn't it wrong ?
Sponsor:
1. One who assumes responsibility for another person or a group during a period of instruction, apprenticeship, or probation.
2. One who vouches for the suitability of a candidate for admission.
3. One that finances a project or an event carried out by another person or group
In my own words - one who gives money basicaly for free (maybe in exchange for promotion of his name/trademark).