They provide (amongst other things)...

  - mentoring (10 weeks in incubator, then ongoing)
  - speakers e.g. Ryan Carson, Joel Spolsky
  - office space
  - accomodation
  - money (expenses & living allowance while in incubator)
  - free breakfast and lunch every day
  - sessions on product management and sales

...and take no equity (atleast initially?), tie you down at the end, or even require you have a company.

Seems the motivation is work with "smart, exciting people" and build relationships with those trying to build "companies where the customers are other businesses rather than consumers".

They describe this as an "accidental incubator"...

  "Over the course of the last 10 months we’ve managed
   to create an accidental incubator.

  After meeting start-ups at various events, we found
  ourselves playing host to about a dozen people across 
  five companies here at our offices. They all seem to 
  like it, and we like them, which inspired us to put 
  together Springboard."

Also, building on a MS stack will probably increase your chances of acceptance if you are applying (as Red Gate, the host company, builds tools for MS software), but I know first hand some of the companies already involved build using other tools e.g. RoR/Scala/Erlang.