I'll answer the question asked. No, there aren't slots to buy. Each developer gets a redemption code for the mac app store that is then locked to the apple id he uses. If you were to have a developer friend download it and copy the app to your computer you could use it, there is no check.
That said, this shouldn't even be considered an alpha version, its a preview and in my usage so far, very incomplete. It still uses the lion updates and packages when doing software update. Oh, and technically its probably considered pirating since you won't have a license for it.